User blog comment:Dragonzzilla/ME3 Multiplayer DLC I Ideas/@comment-1407247-20120501150257

Two words: Rachni, Elcor.

These two races are both known to be able to take part in combat, so there's no lore contradiction.

I reckon they'd make great potential for totally different playstyles for each class eg. an Elcor soldier who is tough but very slow, has very slow melee attacks, and whose powers consist of deploying into an immobile 'weapon platform' mode to unleash a heavy weapon of some sort.

The old Mattock/GPS/Phalanx DLC for ME2 made weapons more interesting by introducing new/anti playstyle options, I think the same could be done with new classes.