Neat. As Jamie mentions, the logistics of moving a heavy robot can be a challenge all on its own so make sure you have folks around who can help lift and shift the thing. How heavy is the shell at the moment?

800W scooter motors would indeed work but you'll still want ESCs capable of taking the pounding. Ragebridges would indeed work though you could use a Cytron 60A like Kaizen, Jibril 1.x and Mean Machine have used in the past if you go for the Scooter optionn. The fans on them are a weak point as is a dodgy capacitor but I can testify that they work. I wouldn't want to drive Ampflows with them but they are an option.

Worth considering a pair of linear actuators for the lifter if the pneumatic option doesn't pan out? I am sure the HW version of Luna-Tic did use some.