are indeed out of question, then i would like to see an DLC concentrating on improving the differences between factions/subfactions and adding more to their characteristical traits.
an excellent idea, even the races are not that much different in my opinion.. almost every tech is the same, most ship types work the same way..
VL ideas, I only agree with the idea their titan should be more like a base, but I think giving it a smaller population, culture spreading, trade income and even a minor metal-crystal income, like it is a mini empire of its own the capital of the loyalist Vasari empire, it would be awesome, though ability effectiveness and firepower should be lowered if this is going to happen.. AND VORASTRA SHOULD HAVE DISINTEGRATORS, they look awesome 
Kostura, bad idea I think, even the current way an OP weapon as you can instakill any homeworld in any moment.. noone reaches there in time if he is not vasari..
TEC is good this way i think, maybe economy could be changed a bit.. maybe remove the insurgency from TEC loyalist if its still there, doesn't fit the faction theme.. maybe replace it with something, like if you have a starbase somewhere it gives a bonus of some kind, maybe 10 percent trade income? capping at 20 percent with the double fortresses. Their trade ships could get +2000 extra hull and 20 extra armor, because why not? Would fit the defensive faction and not a gamechanger stuff. TEC rebel trade ships could get some weapons or maybe an ability like the advent rapture battlecruiser, so if the ship is attacked, it attacks back xx percent of the incoming damage, maybe 50-100% retaliation would be enough, with 2 research. Again not an I win button but would be an interesting stuff, don't harass my trade ships or you will pay for doing so
Advent. Well lot to do to make them different. First of all, ONE OF THEIR TITANS SHOULD USE THE PSIONIC SURGE AS MAIN WEAPONS!!!!!!!! Why beam for both, very lame and boring..? And psionic surge looks awesome, fav weapon type of me. Naturally there would be a damage increase needed, like for the TEC beam. One faction should get a resource bonus, maybe the AR, give them a unique tech that increases crystal income rate by 20 percent, this would make up for the Advent Loyalist extra 10% allegiance I think.. Or give one faction a real trade income bonus and compensate the other with some good but different kind of economic stuff?
AL should go more hull than AR, and more armor I think, that would make a real difference, like give all their ships like 10-15% more hull and +1armor (even if after research, so in the beginning the values could be the same for both factions, only when maxed out would be a difference) than they currently have and reduce shields by10 percent(or give AR 10 percent more research for shields). AR could have increased BASE mitigation, 20% instead of 15% and more research for increasing it, highest level capital ships and titans reaching 85% or so mitigation (for compensation of their low hull and armor). Both factions need overall PM block as Vasari only laughs at their capital ships and titans.. Advent Rebels should have more things related to afterlife, maybe one could be that their capital ships and titans get XP if allied ships are destroyed in the gravity well, maybe 5 percent of the XP cost of the ship, and some context can be made up easily, like the dead crew before going into the light shares their experience of death with the highest rank Advent matriarchs or something..
VR should really be able to build 1-1 TEC and Advent ship type, maybe buy them from their allies? to say VR asks TEC ally to sell them the concept of the xy ship, and for the rest of the game while this treaty is going Vasari can build that ship type, but TEC could decide to end it by repaying the cost or ending the alliance..
