I have SEEN this done. (Wouldn't touch it with a 10 ft pole myself!)
The inside and outside skins can be removed, and the frame, which is cast aluminum can be welded by someone who is familiar with aluminum welding and who has the right equipment. The temperature to weld.steel/iron is much higher. Because the frame cracked and flattened the curve, a jig to hold the frame at the correct angle.must.be built to hold the door frame while welding.. it should be test fitted into.the opening. Once the frame is welded it should also be test fitted in the opening. Only after it matches the curves of the trailer and fits tightly as all four corners and across the mid-section should you re-skin the door. When a door flies open in transit, there is no telling how oddly it will deform, though it is usually worse on the handle side.
I know there is at least one old thread here about welding a vintage frame... and a funny one on how to fashion "the wedge" to prevent a this whammy.
Newer models (approx. 1995 on) have braces made of sort of origami folded aluminum sheet. Ditto for the ribs. They usually bend rather than break, and can be bent back with brute force, a rubber mallet and a couple of pieces of 1 X 4 lumber. There are YouTube videos that demonstrate this technique.
Today is a gift, that's why they call it the present.