Gaming

I wonder if Summoner Eidolons might not just be the way to go then? They come in a variety of forms and Synthesist gives you a framework for how they merge with people. Obviously there will need to be some narrative restrictions in place to make the whole "it's actually a mech" work but otherwise it's at least premade and works with the Pathfinder rules.

In retrospect, I don't know what else Witchburner could have been about lol.