Before I continue, I must say that GalCiv2 is an Amazing game. A game that conquers the competition and whose only new enemy would be Spore.Anyway on to the Discusion.

Stargates, you never see them and yet they are a very important part of the Back Story. So now they deserve to be honoured by bringing them back. But why would you bring them back if you have hyperdrive. Why it's very simple. You combine them to get instant teleportation machine whose two types would be Public and Military. Public would be used to create an intergalatic highway. This comes from the fact that Planet population rises also do to immigration(maybe DL only) and yet you never see a small family size ship that represents the immigrants,tourists,and whatever else. Now with an intergalatic highway with stargate hybids: immigration, tourism, & trade would happen more smoothly and you income from those types of sources would increase tenfold. Now it would seem most there would have to be an U.P. meeting before the player can hook up his stargates with the other alien races' stargates, thus making the highway "intergalatic" in the Diplomatic sense. Now while the first brought the Races together, the second would rip diplomatic relationships to shreads. Military stargates would be bigger and would instanly transport any of your military units to any of the other Military Stargates you bouilt. But beware, because this could become so dangerous, even your best allies would resent it. So if you want to keep the Advantage you better prepare for war.
Another feature which I'm suprise that pretty much all 4x games lack is Education. Education is important for the real world so why not for the 4x world? Education would be fairly simplistic. There would be to bars. The First would represent how much your empire is paying for Public School(Daycare to College) and the second would be how much of the population is allowed to go to Private School(covers the same as Public but families prefer Private more). Now when public school recieves a low amount of funds, it creates a population "lacking" in "brains." Now these citizens in the future would be very easy to keep pleased. So you could have a very large population without worrying much about approval, but the undereducation would negatively affect research and Production. On the otherhand highly funded Public School Students would cause give a bonus to research and production. Still the populace would be harder to please. Then again you can ditch paying for Public School and off all of your students to private school. This would give a Research & Production bonus that public school could never get you, but satisfying the population would impossible to the majority of players. So you would need to find a balance between Public and Private.
Finally, the last request is the ability to see your planets' demographics(age, gender, species, type of Education, etc.) This feature would only make your populations seem more diverse and interesting. Still it should be included because many players have wanted this feature since the birth of the game.
Anyway thanks for reading and if you have any opinions or suggestions, I would really like to hear them so that I can improve my own ideas!