So far I found this recipe suitable for print reversal:

1) Develop in standard developer
2) Place in acid stop bath
3) Wash
4) Bleach in a non-rehalogenizing bleach
5) Wash
6) Redevelop with same developer
7) Stop
8) Fix

The bleach required is made of either potassium permanganate or potassium dichromate in a weak sulfuric acid solution

And I know how nasty the dichromate is... (I use that for Bromoil and I always very afraid of handling that chemical...)

What do you think of it? I have already the dichromate, I don't have the sulfuric acid...

I guess the same procedure for wet plates won't work... But since the wet plate trick is to have a very weak image that appears to be a positive when positioned on a dark surface, why one couldn't do the same with a bromide emulsion? Sometimes I had that effect by chance with badly underexposed/underdeveloped film... How to make that accident repeatable?

As for the idea of exposing the plate under the enlarger: clever, but no fun