in other words, fabricate the flange on the backside of the door where needed?
The other day I did a lower door skin that I fabricated and on the other side I did just that...cut a chunk of the flange out, replaced a piece on the inners and welded a piece back to look like the flange. I also didn't cut it all the way at the bottom cause the metal was ok there so I didn't have to file it down or worry about it changing the gap to the rocker. Saved soo much time doing it that way. Good call.
Funny, I'm actually editing a video on the lower door skin and left out the footage of the repair of the flange being cut out on the other side but after this thread I will probably go back and insert it into the video.