A complete rebuild like that is about where my trailer is - I'm not sure there's much to save beyond the frame, and I have my suspicions there. It might be best left as a yard trailer that takes more of the dunkings but doesn't see road use. Sounds like you guys put a lot of hours into yours, it must be in real nice shape now.
We have a very good trailer place nearby, I might start by taking the trailer specs from the Farrier site and pay them a visit. It seems more people have gone this kind of a route than I thought previously, I had the idea that most just went with the known names (Pacific, FE, Trailex, etc.).