great game, next to SWM the best Star Wars game.
the minis are as good as SWM, but or not painted.so using SWM instead, makes for nicer minis.
I don't see any cross over possibilities though

I've played it. Very different from SWM, as you need 1 player to play the "narrator" or "dungeon master" and the other players play against that one. The Narrator controls imperials and the other plays pick from a limited number of characters. These characters play much more like an RPG that SWM. They can gain new abilities and upgrade their gear. When players trigger certain events (open certain doors, slice a certain computer) the narrator triggers an event, all pulled from the campaign guide he uses to set up and run various missions for the players

Imp Assault feels like a pen and paper RPG (think dungeons and dragons) that has had the role playing stripped out of it, and the rules simplified so that it resembles more of a table top skirmish game.

I believe there is a VS mode for Imp Assault... but I never learned how that works. (I don't own the game, I've just played my friends copy when he ran it for me).

As stated above. The minis in Imp Assault aren't painted. If you are a decent painter, it will be easy to use the Imp Assault minis in SWM (or reverse). Imp assault minis are NICE, and as far as I can tell, are on scale with SWM. They seem to be better made and of a sturdier plastic than SWM.

the combat systems are completely different.
you'd have to change ALL the special abilities, and combat stats from one game to the other.
can't imagine how that would be done

IA is fresh and new, with new releases still coming out.
the greatness of IA, and the lameness recent, and near future Vsets, has soured me on SWM for a while