It's a very attractive-looking shell. If the price were good, it seems like a great candidate for a small camper of your design- no need to follow the original. Check condition of the frame,
axle, floor, and
windows.
Most small, rear-entry trailers of that size have a similar layout: large dinette/bed in front, galley left of rear door; storage,
fridge, sometimes toilet or porta-potty on right. The width determines whether the dinette bed is set up for longways or crossways sleeping, but longways is nicer. You could look up Hunter Compact, Trailswest
Campster,
Havasu, and
Little Joe trailers in the archives for ideas.
In the end you can do what you want. Make sure you use lightweight, RV-appropriate materials and construction techniques, and provide for some floor-to-ceiling shell support on both sides. Pay attention to left-right and fore-aft balance in your design.
Do you have a garage or workshop, tools, and experience with plumbing and wiring? Rebuilding a gutted shell is a big project requiring a substantial investment in time and money. It's almost never the cheapest path to trailer ownership, but it can be very satisfying for the right person.
If you decide to take this on, please start a rebuild thread!