To suggest that the rim is or is not stable is beyond my scope of expertise. That said, I have built a lot of wheel set and I would not use a damaged rim. And I would not try to bang the damage back into shape. I would just replace the rim and I might even have an orphan. The idea of nipple washers would be my next move, were I needing to use the rim. I do have a set, or two of those elongated washers also.

Anyway, if a rim fails catastrophically (can't believe I spelled that right), down you go. Taking a chance seems like an idea worth thinking over a couple of times.