As a shooter fan, I've never seen anybody else who can merge powers and shooting in a way that Mass Effect does it. Mass Effect 3 has very solid core gameplay, and all they need to do in ME:A is continue to refine that and make it better at what it does.
It's also strange that you ask what Mass Effect can do to separate itself and recommend that it just flat out copies another game's mechanic in the same post.
I used Vanquish as an example because it was the most Science fictionie shooter that is mechanically distinctive from other games in the genre, based on my experience anyway. Level traversal is something not many TPS's have experimented with, I'm no creative director but I feel this would be the easiest avenue to experiment with to hopefully give ME:A's combat a unique feel.
As for ME merging powers & shooting, apart from sending peps flying with biotics I didn't find it particularly note worthy. The rest of the talent trees mainly consist of stuns & temp character buffs. Infiltrators can turn invisible but ME's stealth is non existent so it never felt satisfying for me to use.
IDK, ME3's combat focused more on moment to moment action than strategic planing before or during engagement. In ME2 & 3 even on insanity all you use your companions for is spamming abilities seeing as they are useless at anything else. Positioning them means jack & their guns do Fu*k all damage, that was the extent of squad tactics in my playthroughs anyway.
Fu*k it just steal squad control from Rainbow 6 Vegas, slap some rocket boots/ jet pack on everyone & call it a day