Ian;

There is the old standby, Stannous Chloride for reversal. The others you mention such as Sodium Sulfide and Thiourea are really baths that precipitate Silver Sulfide and cause a brown-black image to form. These can interfere with imaging as they can react with the Silver Sulfate formed in the bleach if washing is insufficient.

The Stannous Chloride is currently used in E6 and is not very stable. Before this, E4 used t-Butyl Amine Borane which was quite toxic.

As for overexposure with light, I have never heard of it. If the silver is properly developed in the first developer, you cannot overexpose using light. If that were possible, then the reducing reversal baths would be impossible to control and even worse for this "solarization" effect.

Kodak only warns about overheating the emulsion and causing reticulation, or splashing the bulb and shattering it. The only place I know of that you can overexpose during reversal is Kodachrome processing.

PE