Possibly you can rig up a chain and spring shock absorber arrangement like is used for screen doors on a house.
On my door, the socket for the T-bar hold open thingy is exactly opposite the T-bar holder on the RV wall and that, rather than the door skin, is what bumps. If that's true for you, reinforcing the door in back of that may well be a reasonable improvement. If the T-bar socket is elsewhere, maybe even a large felt bumper pad (such as is used on chair legs or cabinet doors) would provide sufficient cushioning to prevent damage. It probably wouldn't weather very well, though.