Personally, I'd rather like to see that "blueprints" idea used at least once. Blueprints appeared once in a dungeon in GH1, for an old arachnoid mecha that was a predecessor to the Esher or something; they were of historic value but nothing more, as far as I could discern.
Maybe I should try using other skills on that next time I pick it up. No matter.
Still, a quick and dirty interval method would be to create a series of Design .txt's which are nothing more than a torso apiece, with various, well-balanced engines, gyroscopes, and intrinsic armor in Arachnoid, Battroid, Groundhugger, Gerwalk and Aerofighter styles. Of course, you'd have to build them with and without cockpit, just for further customizability so that a person can choose to benefit from having the cockpit in the head. Include no movement types; it would defeat the purpose. Needless to say, this would be a Tech Vulture's best friend.
The single largest problem with this idea, as far as I can see, is that adding so many new mecha would dilute the pool of other mecha in shops, and frankly, most shops shouldn't carry Torsos. Torsos and Blueprints would be for the true collector or designer, the sort of person who loves to micromanage; car dealerships don't sell engine blocks and consoles, they sell cars and offer add-ons.