The issue Willy is that every 4x game I have ever played benefits from expansion. All of them even GCII. The point is that sure you can have a very strong 'small' empire with say 6 or 12 worlds. ..but..the empire with 40 (like the Drengin or the Yor or the Krynn can get) will simply outpace you in all areas, production, research and influence. 

Now we can add special buildings which double, or triple the output of your empire but stop working or scale down in effectiveness after a certain number of worlds are colonized/invaded, but I don't know if that would be fun.

One of the core (..X's..) in a 4x game is expansion and to make a small empire as effective as a small one defeats that. One thing players dislike is a game which artificially limits their choices. We want it all. I want to expand and I want the buildings that work with small empires also in my larger empire. I do not like the brakes put on if there is no way to bypass it. 

In GCII I would expand to about 6 worlds then I was bankrupt (even if I did 20% economy and took the 20% economy government), and i was UNABLE to expand or do anything for about 30 clicks of the mouse. I am not kidding. It would take me rapidly clicking the mouse about 20 to 30 times to get to where I could keep researching or building new colonizers....all the while the ai was continuing to expand without the same brakes. 

I would not mind such rule-sets in GCIII, (I really hated them btw), but if we could tweak how badly it impacts your empire ..maybe reduce research to a mere 20% of what it was, then triple or quadruple the needed production on building ships (dont cut the values I output but instead raise the costs drastically) therefore I am still researching, building and doing stuff but at a far slower pace due to over expansion. 

This indirectly addresses your small/tall empire request. By keeping your empire small you never suffer the ill effects over fast over expansion. 

Perhaps others here have better Ideas. I would love to see them. 

The problem is that with the current system a planet is maxed out pretty fast (all tiles covered with buildings, all buildings have max level). Then you cannot do anymore with the planet apart from surrounding it with starbases to further enhance its productivity.

So the solution would be to have a system in which you can develop a planet further and further and get the resources for that out of itself and/or by redirecting them from smaller planets or asteroid mines or resource mines (preferably with attackable supply routes). Then you had a real choice to make whether to develop a few planets or even a single one pretty far or a lot of planets not so far.

That would be possible if buildings had far more levels or new special buildings would only be available when a planet had reached a certain development level ( e. g. measured by the sum of the levels of all buildings).

To clarify I meant you could add ideas. What I meant is that because we don't know what crusades is like we have to use Mercs for right now. We can use ideas to other games it would be how it would relate to galactic civilizations 3. There were alot of complaints about the game supporting wide, but not tall. No one came up with any ideas on this.

The problem I can see is limited room. Not alot of planets. I would like to see a map with no class zero planets. If you could use class zero planets it could help tall empires. Limiting stargazers hinder tall empires. Maybe something like classifying stargazers, and colonies where there is a limit something like you can have alot of stargazers, but a few planets. A lot of planets, but a few stargazers. Or a little of both. The terraforming option hinders tall empires. The last option should let you terrafom all the tiles. Maybe requiring aquatic water colonization to terrafom water tiles. You could even implement a large empire penalty if you terrafom to many tiles on one planet, or build to many starbases. 

Civilization had some solutions for tall like citizen management like working resources, or specializing in other fields. In call to power you could put them in improvements. They also had a build que that relied on technology, not class. Maybe class could be resources, not how many buildings you can have. 

A solution that was suggested was more upgrades. I did kind of like the idea of a tall ability. If this was a customised race then players could make it. To keep it from being to powerful you could give it a large empire penalty. Maybe the last terrafom tech could be unlimited with a large empire penalty to keep you from being to powerful.  Less starbases for large empires would help. Not a arbitrary number. 

I also don't like the idea of penalizing large empires. Maybe requiring resources to build things would help slow things down.

@ OP: FYI, there was another thread already started on this topic. The good news is, not much had happened on it, so it probably won't make a difference. But here you go:

https://forums.galciv3.com/481142/page/1/#3661896

For further discussion fodder:

Draft definition of Urbanization Ability.

+3 random planet tiles per era, 0.3 base growth rate, +100 % Social Manufacturing, +5% Coercion for each new Colony.  Super effective planets, especially with starbases, but nobody wants to leave the homeworld. 

Since Abilities are tied to races, I would love this Ability to be tied to the Dread Lords.  Give them something to work with.

Good points Pshaw! I just realized we can park 3 rings of star bases around one planet if you get creative. 

I noticed the two points, believe me, but you must be a much better player than I or play on different maps.  I do play on sprawling maps with big empires though, so that is probably part of the dissonance.  On average, how many planets did each of the other factions have?

I still haven't figured out what I am going to do about starbases yet on this Insane map.  I dread the point where I am absolutely forced to decide.  

The one shipyard was probably my empire's weakest spot.  I spent a lot of energy making friends with everyone (and bribing people to declare war on my enemies).  When Drengin decided that they'd finally had enough of me, I had a hard time fighting off their multiple stacks of 4-6 ships while only producing one ship per turn.  In retrospect, I should have invested more in defence earlier on.  

I have a pattern that puts 12 starbases around a planet and am trying that with my homeworld and the precursor factory world. We'll see how that works out.  It is early in the game still, but I find that there have been a lot of relics out there to claim.  It feels like the AI is reluctant to commit administrators early in the game.  Especially on an Insane map, that isn't a particularly good strategy decision.  Those things are valuable.  I have learned to claim relics such that they also claim resources.  A new priority.

One thing I wonder about when it comes to less expansion is how to mine Durantium et cetera at a larger scale. I usually have quite a lot of mining resources and use them heavily in ships. A large AI civilization will be able to do this against me if I choose to play as a small empire. Also you have to consider all research-, production-, ascension resources et cetera. How are a small empire going to compete against large empires on these, if they can´t reach them?

Hey, no sweat man, we're all working towards the same goal. I am sure the StarDock folks would see both of them, one topic just makes an easier discussion. I think the discussion here has been more productive.

I want to look at this a littel more from a game design perspective. At first blush, you are correct that: a) tech snowballing is a problem, especially if you disable tech brokering (which often evens out galactic technology); reducing research as a function of number of colonies might well be a way to prevent it. My biggest concern is coming up with a reasonable (i.e., player-acceptable) in-game justification for this.

I am not exactly thrilled at the idea, but I think it should be considered more fully.

I'm surprised more people haven't brought this up, as this is a fundamental flaw of GC3's mechanics...I do remember a discussion about population growth early in the alpha stage of the game, and I recall most people simply not appreciating its impact...

I would expand on this issue and say that there is too much of an opportunity cost with building farms...giving up a tile for food production cuts into your manufacturing and science production, and adjacency bonuses only exacerbate this issue...being able to import food would help this problem immensely and combined with nonlinear growth mechanics would allow tall empires to be competitive...

I would think unindustrialization is not so effective as it is. I looked it up once industrialisation is on average forty time more than unindustrialization. Production is to significant. One solution would be to remove population caps making the population same on tall, or wide empires. That would fix production not room. One way to fix this is to allow you to terriform all the files.