Ok.
Preparing to state my geekhood... but tis ok. I am proud of it! *fist to the sky*
Space battles, yes... but only if you get ship manuverability like the ships seen in the Babylon 5 series. The ability to spin and shoot behind you in a dynamic space is essential (and logical) to space battles, IMHO. Shooting upside down, creating plastic maneuvers to allow you to fire in any direction... yes... because honestly... in space: what is up... and what is down? it is all relative...
Also would like to see the character customization ala SWG. I like the idea of being able to look at a toon and recognizing him/her/erm... it (Asgard). I admit... I got to where I could pick out my best friend IG by sight- even in full Composit armour! Was awesome.
The ability to earn faction from NPC's and gain unique skills/abilities/tech whatever from that race/species. Aka help the Jaffa and they teach you how to use the staff weapon effectively.. of fight like the Sho'kar (sp?). Or become infested by a larvae.. which would make you have to seek out the Tok'Ra for removal.. but would also gain you the ability to use Goa'uld weaponry... of some such stuff like that.
The ability to affect permanent change on a world. Perhaps instanced to you and your Command? As in.. your team visits planet X and completes the objective- which causes a volcano to explode and obliterate a village. if you ever return, the volcano has still erupted, village is gone, NPC's recall you, and maybe a secondary village is now being built. (I know that is probably far too complex for an MMO.. but was an example

)
Just a few thoughts off the top of me noggin. I haven't read the stuff above (below?) me. hehe