Well, after reading this, and some other thread wich dealt with bigger bases, I have some ideas I would like to share here:
1) Bigger bases (not "infinite" ones!): may be some day could be coded the posibility to add a special facilty called, for example "large base life support", which would have expensive cost and mainteinance... The effect of this facility would be that when you build it, you are allowed to make your standard 6x6 base larger, say 8x8 or may be 10x10 o may be a moddble new base size... So, you can have a large or very large base, but you will have to pay a lot for it (again, this building and fixed monthly costos should be moddable)
2) Two level bases... I don't know... wouldn't it be cumbersome to show such a base in the base managing screen? May be making an "upper level - lower level" button just like the one in the battlescape? I think it would be easier just to have the possibility to scroll around a bigger map base on that screen.
3) For the two level bases, I assume hangars will be only be able to be built on the upper level (or being a double height facility, taking 8 squares (four lower, four upper) to allow the alien raiders to easily get to the lower level of the base. The same will be true for the main elevator shaft, one square area, two squares deep. Will aliens directed by the AI ever invade the lower base level?
4) The "space program base" is an excellent idea... To win the war you will not be able just to launch any ship from any base... but a special spaceship from a special base... Pray for the aliens not to find that base before you can equip and laouch your final assault!
PS: I would love to see what is explained in points 1 and 4 included in the game, or, at least, some similar thing!