I think having an engineer class would be pretty sweet with different kinds of gadgets and do-dads. Super could be placing an auto turret, but the subclasses could determine its damage and how it fires. Solar could fire tracking missiles with splash damage, arc could be your standard high RoF with chaining or that provides a small shield, and void could be mini nova bomblets that detonate after a short period unless directly impacting the target. Grenades could be (just examples for the element, not meaning each element on all) trip mine, suppressor, and flux? Melee could be some kind of throwable remote detonation device, similar in practice to smoke, with different effects like flash, trip-mine esque, or just more damage. I mean, I'd be cool with it xD