Quick update: Built a prototype out of scrap wood and whatever else I could find, and got the robot running with the Ranglebox Saturns/ESC/motor combo! Videos/pictures are on my phone so will upload when I'm feeling less lazy :P

So far its invertable and has a low profile, I cut the plastic base plate out and have just fitted the gearboxes in the proper place. Next up is cutting out holes for the wheels and starting to build up on the real thing. Hopefully the weight of the final chassis is low enough that adding a lifter/flipper is not an issue.