Let's assume the engine is ok (which is not and will not be), Ilum would still suck big time. Just recall what was happening with the faction imbalance in early 2012... one faction camping the other base entrance hoping for a lucky kill... that's not open world pvp, it's a joke. Unless they can actually come up with some really objective based open world pvp other than "capture this point" there will be nothing worthwhile but warzones.
Dunno about you but my game performs night and day better now than back in those days. There is alot of random NPC stuff going on on Ilum(the removal of which could be part of their fix) but I see no reason why the game cant handle 30ish v 30ish. I've seen some pretty big fights in the black hole without any lag.