Knowing you, you don't want too much bigger because then you'll start limiting yourself on where you can go with it. Remember me at Area BFE with my popup? Sure, doing a SOA on it would have alleviated many of the concerns and probably saved the landing leg that I ripped off on the way out, but still IMO you couldn't get much bigger down where we were.
You are going to have to compromise because you want to bring a lot of toys (don't we all?).
I know the tops of the popup can't support much weight, not much more than an air conditioner or a bicycle rack but could you build something that would allow your motorcycle to ride up top, more centered over the axle, that would still allow you to raise the popup, and not be a complete cluster?
I was thinking something like those racks they make for Jeeps that you can use with a soft top or not top. Might add an unacceptable amount of width though trying to tie it in to the frame...