Why not allow customization of the generic repetier, delta, and marlin profiles to start. I have a feeling most of is fall into those brackets.
You would need to allow users to setup:
Custom X, Y, and Z limits, max temperatures, number of nozzles, cooling fan enabled, heated bed, extruder offset, home coordinates, and filament diameter. Those are the big ones, the rest of the important stuff seems to come from the generic profile and match up automatically already.
Eventually you could add editable start and end gcodes, z offset, and events like pause at height and tweak at height (adjust fan / temperature / insert gcode options).
Your announcement of this update brought me back to 3dprinteros. I really hope this works out.