I'm interested in what others can offer for solutions, but I think it's going to be tough.
One method, is to paint some nice phillips head screws and just screw them in there.
--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The Place to go for Pinball Repair Info

Some quick googling seemed to point to bondo for filling and this for painting:

http://www.treasure-cove.net/coindoor.htm

Grind, weld, grind, smooth, blast, powder

Looks fine to me... shows the machine has been out there in the real word, and gives it character.

A little touch up paint (or optionally repaint the whole door) and you'll barely notice it.

-Mark

you can try some jb weld like this coin door repair:

Gonna be pretty difficult to make that dissapear, as you can see the metal around the holes is all distorted. I would just replace it, easier and better results

You'd probably have to grind it down, then fill.

I fixed a coin door that was as bad or worse. I flattend the area out with a hammer and dolly, ground it down welded up the holes ground the welds flat, applied a little bondo, sanded it all down, primed and then painted it with Rustolium Black Textured spray paint. I think it turned out great.

WP_0005701.jpg

DSC00578.jpg

DSC00581.jpg

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Take it down to your local custom motorcycle shop (community college, auto shop or anyone who does welding) and they'll weld it for beer money. Flatten out the area and do all of the prep beforehand so all they have to do is a couple of minute weld job.

Don't expect them to do it right then, but ask when a good time to come back is. They may not want the boss around, will prefer to do it quickly before lunch, etc.

Bondo, JB Weld or any type of filler is not going to last unless you also adhere a backing plate on the inside of the door.