The Raven type would be a good start. Perhaps as a heavy engineering craft. It would be equipped with shield extends and hazard emitters, and be armed with some kind of point defense phaser and micro-torpedoes.
I've never heard someone suggest an engineering style pet but I can't help but admit it sounds like the Feds. A pet with EPTS, Engineering team and Extend shields 1 could be pretty decent. I don't know what kind of offesive powers would make sense besides beam overload or AP:Beta.
The Feds do have a Engineering Pet. The D'ykr Vulcan sci ship has a smaller ship that detaches from it and uses Aux to SIF on you or a target. It'd be nothing to add in a more Feddie style version of it for carriers. Which works a lot better than a Defiant or some other combat frigate. Give it some decent hull but crappy weapons and there you go.