Those "egg" trailers are incredibly tough, but, they also cost. I looked at the Casita and Skamp when we bought our FunFinder. Light, all fiberglass, incredibly durable and wouldn't work for us in any way, shape or form. They have their uses, but, for the money they command (like Airstreams) and what you get in space, ammenities and comfort; I'll keep my FunFinder with its slide, walk around queen bed and dry bathroom with lots of tank and storage space for less than half the cost.
Even with a whole new roof, you'll still be coming out cheaper than the initial cost of one of the all fiberglass trailers and all fiberglass has some drawbacks also (I know, I had an all fiberglass cabin cruiser back in the '70s...it is true; just a big hole in the water you keep throwing money into, RVing costs pale in comparison).