Right -- which is why I want to leave it where it is if at all possible (reference crankset position and chainline). At this point, I think I'm going to try fit a few different front derailers and, if one of them works, I'll just need to put one of the clamp-on cable guides on it and run it without those short cable sections. This Sun-Bow derailer has a narrow cage with completely straight sides to it. I imagine a more modern cage, with the various shift-enabling contours to the cage, would help push the chain far enough inboard to make that shift to the small ring.

Because there's at least one response that said a different derailer would probably work with the current chainline, I'll give it a shot. One of my local bike shops has a pretty good selection of used parts in boxes in The Back, so I may hit them up at lunch today and see if I get lucky.