A few thoughts. IMHO most "ultra light" trailers are not the type of RV I'd want to make to many changes to that might impact the structural integrity of the walls. I'd also had that I don't think those types of RVs lend themselves to full time use, a long summer maybe, but living for a long period of time I can see being problematic.
Toy Haulers are a plus for ease configuring for your needs, but do keep in mind that most all toy haulers have a heavy pin weight. Depending on your truck you can really top the scales, so do your homework. Without the weight in the back the unloaded pin weight is often more then your average truck is capable. of.