I guess it all depends on how much work you want to put into it and how pretty you want it to be. One thing you could try would be to remove the window (ie., drill out all the rivets in the frame), and try replacing the broken glass with some kind of flexible acrylic--might be tough finding plastic that will flex that much. Then again, if you intend to put a patch over it, you should remove the window frame anyway just so that the patch will be flush with the skin.
The window is in the compound curve section of the trailer, but there is a chance that you could lay a flat piece of aluminum against it and at least get it to make enough contact that it can be sealed up. Again, probably not very pretty.
I rebuilt the wing windows in my '73 GT as single paned windows, you can see what I did if you search for "wing window rebuild," I believe. There is also a thread on here somewhere (I believe it was a full-monty restoration), where the owner of a 70's vintage AS with the smaller wing windows successfully removed and patched them up. I don't believe he did anything to accomplish a compound curve in his patch, and it turned out looking pretty good. I want to say Zepellinium was the poster, but I might just be making things up.