I have a strong preference for egg trailers on the 60s pattern (Scamp, Casita, Escape), if I were to downsize. I've also looked at hard-sided folders (giving up a few more amenities for lighter weight) and van conversions.
Unlike your case, I would be downsizing, so the economics of the jump are different. What I have now greatly exceeds my needs, and is more expensive to move than a smaller camper, but I can probably move it another 50,000 - 200,000 miles for what it would cost me to downsize, when I consider also costs of moving whatever I choose as a replacement.