Photo Engineer felt that dichromates were safer than permanganate. He felt that the risks of dichromates were easily mitigated while he worried about how strong an oxidizer permanganate is. He was also very worried about accidental combinations with other common darkroom materials. He didn’t mind having dichromate in his house but said he wouldn’t have permanganate in it.
Safety is a difficult thing to quantify. Clearly all three of the chemicals being discussed need to be handled with care. I haven’t tried B&W reversal processing myself but I am interested. Reading the different discussions here makes it seem like good results are certainly possible but it does take quite a bit of testing to nail the process as compared to negative development. If (when?) I try my hand at it I will most likely do it with the hydrogen peroxide/EDTA bleach that has been discussed.
In a previous post, I described how to develop your own black and white slides using a simple bleach based on hydrogen peroxide and vinegar. This post is about an improved bleach that has a number of advantages over that one. There are a lot of patents out there from the 1970s through the late...
If I couldn‘t get that to work I’d just go the dichromate route with a reducing agent like citric acid to least make the waste less toxic.