Maybe you can find a stainless steel brake line that is longer and can go right into the back of your caliper, and bypass that little piece of caliper hard line that the bracket holds? I think they make kits like that for the GT4 now, but maybe you could get one for yours?
Or get a replacement wheel carrier from Woody, I don't think they are that much.
I have a set of these brake line bracket studs installed on my car, so I don't have to remove the bolt that gave you trouble when I need to remove my brakes:
Brake Line Bracket Stud Kit
Depending on how much hole you have maybe you could get a short stud and epoxy it in on top of your broken bolt and put a nut on it to hold that brake bracket?
Depending on the geometry you might be able to drill and tap a hole next to the broken stud - and then loosen and rotate the caliper hardline bracket to line up to the new hole?
Just brainstorming out loud...
Good luck!