"IF" Sins 2 is to be coded in 64 bit (which it SHOULD be) Then the number of playable factions will not be an issue at all. Nor will any sort of "2 gig" limitation. The game will only be limited by your hardware. Which is what was intended for Sins, but over time failed, because of the jump from 32 to 64 bit machines. The age of 32 bit was starting to come to an end when Original Sins was released.
Most RTS's until now were limited to the 32 bit standards. So they were more or less limited to 3 factions due to hardware, and software limitations (with the exception of the dawn of war series). That is just speculation since Dawn of War proved you can have many different factions in one 32 bit game, and it still ran smooth. Granted those extra factions came from expansions.The models, and textures are pretty low res compared to sins as well.
I think the reality is there was not enough time. Time to create more factions for these games. Being a model, and texture artist myself i KNOW time is a game company, and artists worst enemy. Time to make concept art, then to model, texture, import in the games proprietary format, do voice overs, add music etc. etc. Then create a UI, and other finalization's of said factions. Then balancing, and play testing. This takes LOTS of time. Even with a large art department it may be time that the game developers just do not have. With the "next big thing" having a release deadline of yesterday thanks to greedy publishers looking to make a quick buck... Who cares if the game is good or not, or if it even works, or not. Making more than 3 factions may not be realistically possible in the limited time allocated to create a new game. That is just my thoughts on it.
While i like most of the ideas posted, It seems most want more RTS in Sins 2, or a new expansion than 4x. Making it more like Homeworld, or Homeworld 2 than Master of Orion 2.
I would like to see IC implement some of the original ideas they had for Sins, but couldnt do it because of limitations at the time.
Like multiple orbiting bodies (planets, moons, asteroids etc.) True Solar Systems with structures orbiting the planets, moons, stars instead of remaining stationary after construction. To add more strategy on decisions on when is the optimal time to strike. Also when would be a good time to dig in, and fortify.
Get rid of the phase lane system.. Originally Sins was supposed to be an "open" universe. The devs did away with it, because of a perceived "Whack a Mole" syndrome in the gameplay. If an open universe was implemented along with fuel usage (antimatter), and range limit from nearest 'friendly" planet/star base like in Gal Civ 2, It can be done, and this will add more strategy than take away. It will also add to the 4x element.
Better diplomacy (than even the diplomacy add on). Diplomacy IMO is still very limited compared to most other 4x games. Spys, and espionage similar to gal civ 2 would add a lot to Sins.
Ground Combat... it doesnt have to be complicated. Imperium Galactica 2, AND Gal Civ 2 had a simple yet effective ground combat system. With Sins 2 you shouldn't have total control of a planet until you send in the MARINES, and have a military garrison on the surface.
Add some more focus on Exploration, and Discovery. The current system doesnt really feel like i am exploring much of anything. Except what is on the other side of the phase lane.
More to say, but i am tired.