Structurally, it's probably fine. After all, if you stand on our FRC robot, it'll probably survive.
I'm more concerned about electrical strength (if that's a thing). There are no motor controllers, breakers, etc. Running 3 CIMs on a 150lb robot is already a risky thing, so I figure running 3 CIMs on a 200+lb scooter can't be healthy.
Now, about the CAD model: the front wheel can't spin right now, but I'm sure that's just CAD. Also, it looks like your life would be so much easier if the front wheel is dead axle(edit: to clarify, dead axle would get rid of the front wheel brackets and a couple of bearings). I like how your CIMs are supported from the back, but I'm not sure how you're going to get them in and out if maintenance needs to happen.