well, the right way was noted in the post I linked in my original post; it involved removing a bolt so that the pivot was loose, etc... I 'studied' the problem long enough to realize that with some gentle but steady pressure, the cage could pass its stop (which it did) without applying any sideways force to the cage itself (as I wanted to avoid bending it any more than it might already be).

It still looks straight, and it lines up nicely. Everything shifts well when not under load. Hopefully I will get a nice shakedown ride in on Saturday, at which time I'll either cheer for my success, or weep in defeat and go buy a new Derailleur (and chain, and cassette... I hope I don't need new chainrings....?)