Complex multi-part procedural missions is what's needed. Not just for engineers, but for the BBs too.
Repetition needs purging from all aspects of this game.
For the Engineers, I don't think they need to be procedural. They could be complex, well made, and completely hand crafted. Why? Because there's a relatively small number of Engineers in the game, and you only have to unlock, gain access to, and rank up with each one of them once. So that's basically the number of missions you'd have to craft for a mini-campaign anyway.
And since each engineer has a sort of theme to them, or at least an area of specialization, there are lots of good creative jumping off points. These handcrafted missions could also sort of serve as more advanced versions of the tutorial missions, exposing you to some of the depths and nuances of different styles of play that you might not have learned about otherwise.