You may not want to go down the road of a complete strip down, de-rust and rebuild with a new skin, but I'll write this anyway just in case, and for the benefit of others who may want to.
My door was worse than that. Plus the skin was cracked and holed around one of the wheel carrier mounts. And this has the bigger triangular mounts. I removed the skin and had the frame shot blasted and zinc primered. It came back looking lovely. Then I drilled some strategic holes and injected Dinitrol. I got some galvanised steel skin panels to refit. It wasn't too bad a job to fit them. You need a big enough table to work on. Fold the edges over a bit at a time, working backwards and forwards. I used some polyurethane sealant as a jointing compound. Once the edge was tapped over as far as I wanted to go using a hammer, I used a sturdy G clamp with some protective strips to crush the edge down to its final position.
After carefully working out where the lock hole should be and cutting it out, much to my annoyance I still had to move it sideways a bit. Fortunately the plastic insert on the rear side just covered it up.
On the inside of the door I bonded some reinforcing plates in the recesses where the wheel carrier bolts came through. You might want to consider an alternative type of wheel carrier to the one you have, depending on how you value authenticity over practicality and door longevity.
Removing the glass to carry out the blasting and re-skinning started out to be a major problem. I struggled and failed to release the sealant holding it in, and started to think that the only way it would come out would be to smash it and chisel the remnants out. Then I tried my vibrating multi-tool thingy. I used the plain knife edge tool. At first I thought the vibration would crack the glass but it held up. It easily cut through the sealant to its full depth and the glass came out with no trouble at all. If you haven't got one of these tools then get one. They are surprisingly useful for all sorts of jobs.
