Something I’ve been toying with the idea of is having an engineer that can deploy a modified RC car, and then drive it around. It would be a small, quick little thing that wouldn’t have a lot of health, and wouldn’t have any offensive abilities. But it could be used to disarm/arm c4, disable deployables like Proxy’s mines or Bushwhacker’s turrets, and even carry around the objective, though whether it should be able to deliver it on its own is up for discussion.
As for weapons I’d like to see an engineer with something other than shotgun and smgs, but considering they have to be right up in the thick of things for objectives, perhaps that’s for the best.
Placing the bot would be identical to Bushwhacker’s turret, in that placing a second one destroys the first. Her E could be used to then drive the bot around, and pressing it a second time will pop you back into controlling R.C. again. While it shouldn’t be able to move while R.C.'s not controlling it, it should be able to complete tasks like repairing or disarming without her doing so, after it starts. It should also have a maximum range it can travel away from R.C. before it becomes unresponsive, though if she moves back into range it can be moved again.
This would be fairly game breaking on missions where you have to repair the EV, so it probably should not be able to do so, but things like the tunnel pumps on Terminal or the barrier generator on Bridge, it should be able to. As for the repair and disarm rate, it should not have the increased objective rate that engineers have themselves. You have to leave something for them to excel in after all.
That’s all I can think of at the moment. Might edit this post if I think of something else.