OK, I'm fairly new to GalCiv IV, and have only been solo-playing (on dead simple levels too), but be that as it may, I've seen some gameplay issues that should be looked at to improve things - especially in long-play/big-map scenarios.

1) Nomenclature - there is no naming mechanism for the sectors, and there really needs to be one. There should be a flexible option in the UI to allow for auto-magically prepending/appending the sector name to the contents (stars, planets, starbases, shipyards, etc. - but NOT Fleets!) Better yet, allow US name the sectors so they're relevant to US!

    The WHY of this: You've been playing this game for a real-time-week across 12 or so sectors, and in a monthly turn, the 'XXX' shipyard prompts for being idle and jumps right into the shipyard screen. Well dangit, is this shipyard the one for the XXX shipyard in sector Alpha, or the one named close to 'XXX' in Delta sector? I haven't been dealing with those systems for days/yyy-game-months now, and I don't recall the danged names that well! (When you control 30 or 40+ star systems it gets that bad, but then I'm kind-of old too.) With the sector-name (optionally) prepended/appended to the names, this confusion goes away, allowing for better/quicker game play.

1A) (Nomenclature - part II) - Fleet Names should allow for us to specify a naming template (or one of several). Suppose I'd like my fleet names to reflect their contents? like a fleet with 2 dreadnaughts, 3 battleships, a Carrier, and Cruisers (for naval combat) should be named something like "TFNav - 2D3BCa#Cr"; or an invasion fleet with transports and siege ships may be named "TFInv - [Ship types and counts follow here]" - and so long as those fleets remains intact, the name stays the same. For this to work the fleet names have to persist orbiting at planets or starbases. Combat casualties can result in name changes to reflect the new (reduced?) ship counts (reflect any automatic name changes in the event log) Other possible naming elements may be either the origin point for first forming the fleet, any user-defined string element.

    The WHY of this is simple: with 12 (or more) sectors and fleets streaming along from one active area to another spanning several sectors, quite possibly, keeping track of what is where becomes a more significant issue for game management. Having some flexibility and reliability in fleet naming schemes can greatly help in this task. Being able to just click on a roving fleet in the UI and instantly see the name "Ah! THERE is my invasion fleet!" would also help speed up gameplay.

2) Ships/fleet list in the UI - we need some improvement here. It's just not well-suited to some repeated tasks like:

"Yikes! I need a starbase put over here right quick - where are my nearest Constructor ships? ...or do I need to build one?" or 
"Oh, here's a defended Anomaly - Where are my nearest (surviving) Flag Ships?"

Yeah, the existing filter options are just WORHTHLESS for situations like those...and they can happen OFTEN in a long game.

3) Oh, and Flag ships? what's the idea behind restricting their construction arbitrarily? it doesn't make any sense. Why not let me build as many as I want? (OK, I can only build ones without commander slots - fine! same net effect as not assigning a commander one.) You want them to be rare? Fine make it so you need a rare resource to build them or REALLY EXPENSIVE in resources/credits to build one. But...if I can afford 30 of them, well, my choice, isn't it? It SHOULD be! (Swiping "other teams' anomalies" should be a valid in-game strategy, and well, combat losses happen to flagships...ah well, build another if you can afford it.)

4) Secondary-level skills for ALL citizens need to be made available.  I saw the hints for Economist in the UI, and there should also be ones for Farmers (Plant Biologist maybe?) and Workers (Production Manager) - Entertainers have Celebrity, Scientists have Quantum Physicist already (and what the HECK is "Invisible Hand" tech, anyway? that just sounds ridiculous). Restricting the # of supported trade routes to some special species trait or anything like that is just wrong-headed. Make it expensive to buy more of them, sure - optionally some species traits might make them a lot LESS expensive - so there can be roving traders). Also, about Trade - your central concept is wrong. Trade benefits BOTH parties in the established trade route - or the "recipient" has no reason to participate in the trading.

4A)    Real economics never works any other way (at least not for very long). Also, intangibles like 'send us some tech hardware (or knowledge) or resources and we'll send you $" are also fair game for REAL Trading - and that should be part of the in-game economics too. Oh, and those conditions may be changeable over time, too ("Yeah, we needed Elerium for this trade earlier, and now we need Antimatter instead."). There should be nothing restricting transacting fractional resource amounts in this regard, too: i.e. "this month this trade route was worth XX Credits and 0.2 Elerium".

4B)  We should be able to drop and/or re-assign a freigher/trading-route once it's established VOLUNTARILY. Right now, the only way I saw to break a trade route is to invade and conquer the planet I was trading with. Other mechanics are needed (especially if later trading options become viable - below).

5) Production Issues. When I have 30 shipyards, and a month pops me into the "hey this one's idle" cycle again, it'd be really nice to be able to (optionally, of course) designate WHY I'm building something for any particular reason, like: I'm pushing this constructor into the queue in this shipyard to go "over there" - which is great, except that I'm thinking that WHEN I'M BUILDING IT - and I may have forgotten (or been subject to changing game priorities) when it gets DELIVERED later...and forget to intercept it before it gets sent off to the standard destination (wherever that may be) when it is delivered. So, at the time it's ordered it'd be great to have an optional means to designate a "Special Delivery" location for any item in the production queue. Let us get as granular as we like with it. I'd suggest adding a context menu "Special Delivery" button for this to the options when we select a queue item. BUT there also needs to be a visible designator that one's been set into the queue (so we can see it to change/remove that designation if we need to).

6) Diplomatic options: There should be options to trade them Planets/colonies for concessions also (or, more to the point, DEMAND that they surrender them to you...or else!). Such demands or territory-surrender options should carry some serious diplomatic penalties, of course, but, well... Let's not forget our History with Neville Chamberlin and the Sudetenland, shall we? There's a valid lesson for the game in that example. I saw a system was going to turn over to an opponent earlier in the game, and I removed ALL my planetary improvements and orbital structures and pulled everything I could out before it happened. So, something like the Soviet "scorched earth" strategy (or tactic) needs to be an option in the game (if only to force some additional economic damage on them for forcing the issue).

7) Oh, and "Threat of War in xx Months" is another tool for the diplomatic pouch in general (not just for demanding territorial concessions). I will leave it to you to figure out the ramifications, diplomatic and economic, for resorting too hastily to such threats. (One easy suggestion would be: using the option requires xxx diplomatic points to initiate, and on success, no more points are lost, but on failure to follow through, even more diplomatic points are lost - for starters.)  otherwise - what are Diplomacy Points worth/for in the game, anyway?

8) Ordering things in Shipyards - This is a "UI excessive Click-y-ness" issue. There should be a simple way to order multiples of any item without clicking your fingers to death to make those 30 scavengers get into the queue - so I don't have to bother with this shipyard for quite a while! (think about scarce resource times in a long game for why this might be a good idea).  For that matter, a "Skip the shipyard for xx months" might be a worthwhile option to add as well.

9) The Galactapedia is a cute idea, but ONLY if it is COMPREHENSIVE. Try finding "Economist" or "Invisible Hand" in the current Galactapedia...I'll wait...what? nothing there?  If it's in the UI, AT ALL, it danged well needs to be covered in the Galactapedia - even if the description has to read as "NOT YET IMPLEMENTED AS A GAMEPLAY OPTION" Either make the UI and Galactapedia contents match or make sure it's removed from the UI COMPLETELY. Nothing half-baked like these examples should be in a published game people pay for. Consistency is needed here, people.

10) Tech Research - 2 points here:

    A: if there's supposed to be a Ministerial option to affect the # if items that can be simultaneously researched, then that option either needs to WORK (let us assign % of research points to each research queue), or the promise of it shouldn't appear in the game.

    B: When the LAST item in the researchable line is reached - there is nothing to let us know what happens NEXT, exactly. It SEEMS like final skills in shields, weapons, warp speed, cultural expansion, and one or two others allow us to keep on researching those techs ad infinitum...but to what end? It is visually and, well, generally (actually) just unclear what's happening there.  it would be one thing to have to research any particular skill/area of technology to some minimal skill progress point to open up the "next level of tech" in that line, but if additional research enabled greater benefits for the resulting tech, then it should be so for ALL Tech skills (not just the last ones in the list).   For example, if I had to research Exotic Energies to, say 40% to open up "Cloaking Devices" for research, OK, now I can research Cloaking Devices. BUT the effectiveness of my resulting cloaking tech is affected by how well those preceding tech areas have been researched and mastered (or not) 50% mastery of Exotic Energies will yield better cloaks than 40% mastery would. Getting to 100% on any tech should be VERY difficult and time consuming, so you have to make the infamous "Engineering Compromise" choices here too

This would provide a Very Good Reason for supporting multiple research queues - some for new techs, and some for making older tech better, too.  Absorb that thought a moment, then now revisit 4A (above) a sec...Now we can add the game mechanic that I can request "Exotic Energies" research points as part of the trade route too (the kicker is that it can only be effective if the trading partner has points there to share in trade - and that may all require a Research Treaty to be in place as well)

Ok, that's enough for now, I think.