I like that idea of carpet on plywood.
I have a low spot after not being careful when we first got the MH. I think a rafter ( cross piece) is broken. I opened the ceiling and found these cross pieces are a little smaller than 2x2's. Half inch plywood over them at the back but not at the front. Now I use planks stretching across the roof to avoid putting my weight on the cross pieces.
If you can find an easy way to look inside the roof you will get an idea how strong it is.