Even if you beef up the suspension I think you'll probably still be over GAWR in the rear, and probably GVWR too. I know there are some ultra light ones that can fit in a Tacoma that I've seen advertised but IDK about their size or construction to know how suitable they'd be
How many people are you looking to sleep? I've seen some pretty innovative camper setups with a regular topper. But the Rambox bed still poses a problem for you. Don't get me wrong, I love my Ramboxes as well, but I knew that getting a topper/shell would basically be out of the question for me now.
This video has been floating around the Forumz for a few years now I've seen: