Had a this thought. Not everyone will like it but here is the thought.
We make the Bomber model a repair vehicle. I'm not saying to scrap the Bomber entirely. But like the Dropship we can modify it so that the Bomber instead acts as a mobile repairing vehicle for larger human vehicles.
Just to be clear, I still want an engineer unit for infantry that can also repair vehicles.
But this is just another way that humans can repair their vehicles, perhaps even more effective than a single engineer.
Expand the bomb bay size/opening so that instead a repair laser/beam can fire from it. The Repair Ship/Bomber model just flies over the damaged vehicle and begins repairing. It flies away when its job is done.
Alternatively, it could also serve as a Vehicle/Tank Transport if the model were modified. I prefer Repair Vehicle but this is also a decent idea.