2) Feature scriptability (essentially, allow features to use scripts exactly like units, for animations and such)
2b) If not feature scriptability, than ability for a "nuetral" side with real units.
3) Option to NOT use silly green glowing blobs of nanoness.
4) Behavioural/Situational AI scripting abilities -- in Descent: Freespace you had the option of scripting behaviours and actions into units.. ie, tell a ship of yours that if a certain enemy ship was destroyed or heavily damaged, to do something, like leave, or board the ship, etc. Basically things like, if your Commander is being attacked all nearby units will automatically move to defend it; or another such as if a certain enemy unit is encountered, a certain unit of yours will move to intercept it (ie, a counter-unit). I do not know anything about Spring's AI abilities and this all may exist. If it does, yay!
5) Proper interactive GUI interface map-making program! gogogo
6) "Prerequisite" tag in FBI (like C&C) that dictates that a certain unit needs to be created for that unit to be able to be built.
7) "NumberBuildable" tag in FBI that dictates only a certain number of this unit can be built (as opposed to painstakingly setting build limits in mplayer settings. Also this would be universal).

9) WeaponAmmo#: Dictates how much ammunition a unit has for its weapons, after which something will happen... like it just doesn't fire for a certain amount of time or some shit. Good for things like bombers, tanks, etc.
10) Couples with WeaponAmmo#, AmmoRestock#, which sets how long the unit takes to restock its ammo after running out.
11) Script support for forcing a weapon to fire outside of the aimweapon portion, though this is rather specific for a personal need of mine and I don't even know if this is possible already (is it? *looks at zwzsg*). It's for C&C drop pods; when they land to unleash troops they unleash a barrage at the ground underneath them to clear the area before touch-down.
12) Setting different kinds of flying units, somehow, with an FBI tag. I know in TA if you had a flying unit it was treated as an aircraft reguardless of if it was actually just a flying rocket KBot or something. For me, I need to make Jumpjet Infantry but I dont want AI sending them patrolling around the map with the aircraft.
12b) Alternatively, just an FBI tag linked with hover units telling the game that this unit ignores obstructions and features.. as if it were able to hover above trees and stuff, but not be an aircraft.
Okay that's all I got for now. I have to go take a shit and then head to work.