All good points. Especially about building a coffin - I had zero woodworking skills (I had never used a saw, sander, etc.) before I did mine and I think it turned out OK. But I can understand your PoV - I felt the same way when planning out my build.
As far as framing it, I would steer away from directly skinning the freezer -
1) Build a cart with wheels - this can be as easy as a few 2x4s with casters on them
2) Put freezer on the cart
3) Build three panels from plywood
4) Connect those panel to each other and then sit the "frame" on the "cart"
Bingo! Nothing connected to the freezer at all.