I think there's a lot of great ideas in this but I have to agree with Phil. Adding a lot of weight to the top will make it pretty tippy. Our Sunrader has the original 22R engine in it and it's SLOW uphill. Most toyhome owners strongly advised us against towing anything substantial behind them since they are already underpowered by today's standards. Are you thinking you'll be transplanting in a new engine?
Absolutely will swap the engine and add rear support. Nothing over 1500lb would be considered. The photos are not realistic just some concept art I was playing with. I appreciate the concerns though. I'm not planning anything from this.