I think the advent and/or tec might get some sort of repair ability, since none of thier capital ships have a hull repair ability.   Vasari might get a shield repair, for the same reason.

Advent and vasari could prolly suffer to gain another interupt ability.

All the races could prolly suffer to get a second anti-strike craft ability.

Advent could suffer a non-ultimate bombard ability.

Vasari and TEC could get some sort of AOE fleet buff or nerf. 

Vasari could totally use some sort of antimatter manipulation ability. (Advent have disciples and antimatter charger buildings, TEC have epic culture, starbase resupply and donov flux field, Vasari have... preety much nothing).

There are no abilites that affect shield mitigation in a positve way. might see one of those. doupt advent will get this, and need to be carefull to prevent 100% shield mitigation.... Say, a tec or vasari ability that sets the minimum shield mitigation to 65/70/75% might be cool. wont be very helpful for the capital ship, but will keep the fleet alive better.

3 more ultimates...

no idea.

I, for one, am in favor of giving late-game pirates a custom capital ship. 

It would actually be a behemoth mining ship converted to combat duties. The weapons would then be related to its past as a mobile mining station.

It would be heavily plated and weaponized for its pirate duties (the standard weapons it will use in combat, whichever they are).

For its skills, it will mostly have repurposed mining gear:

Huge tractor beam able to freeze and pull ships. Once the beamed ship contacts the behemoth, it is boarded and permanently switches sides to the pirates. 

A close-range series of disintegrators would also be in order, since the ship is suposed to have a large set of drills for its operations.

An EMP-like weapon is very piratish, having an armistice-like effect, disabling all weapons temporarily, making time for a handy escape.

Lastly, mines would be a nice addition, which would be meteor-smashing charges repurposed to be left behind as a way to disencourage persecutors.

Multiple times. The zombie horse has been beaten repeatedly.

i could see the new caps giving each race some of the abilities of the other races.  it has been long enough and enough ships have been recovered to be able to do such research.

does anyone have a time frame for the new game.

This speculative remark is the best one of the thread.

You, sir, have won the thread.

corvettes will probable be bombers with a jump engine strapped on.  ie no carrier, but then again they could be a frigate without a jump engine then you would need a carrier.

I want an Urquan Dreadnaught.

...

Just kidding. Honestly, I think Lead Head's (which isotope bro?) idea about the other races getting 'scout cap ships' and Vasari getting a true 'support cap ship' sounds the most likely. Although I'm resistant to the idea until they get the Marauder "right". It's still got a useless ability dragging it down. Subversion needs moar epik.

Whatever they do, I hope that each race's version keeps the trend of being markedly different than the others in theme.

As I said before:

TEC: A support / defense capital ship that scales well with large fleets and late-game combat.

Advent: A true dreadnaught class with vicious firepower and an accessible planet-killing ability.

Vasari: Something unique that isn't in the game yet (Vasari capital ships already have very well-rounded roles); I vote for a mobile-factory type capital ship that brings the industrial facility to the front-lines.

The TEC starbase can already manufacture, I don't think it makes a whole lot of sense to give them another capital ship that can do it too. It works once, but the second time is like "Well.. couldn't they think of something else?"

I would like to have this for modding. But right now it would conflict with the UI (overlays fleet management buttons) which I'm not sure if they will change with this expansion.

They already have multiple support and defensive capital ships.  No point giving them something that already exists.  The new capital ships should bring something completely new to each faction.

Again, that was just an example of what I meant.  I wouldn't want that exactly, I was just rearranging the ships you provided in a way to illustrate my point.  I do not want the weaknesses resolved, I want the strengths exploited.