I have tried this. It works but wasn't sure about the density so I recently did the following test using Foma 100, 120 roll. I made exposures at 100, +1/2, +1. I developed in Suprol 1+4 for 6 mins. After bleach and clear I split the reversal part. The first 3 frames were exposed to light then second development and the next 3 with Iron Out, two teaspoons in 400ml water.

When I was doing the development the light reversal strip developed blacks very quickly. With iron out the development took longer and whilst the film was wet the blacks looked less dense but when dry there was not much between them.

I have enclosed scans, I know this brings in other variables but it was the same parameters for both strips.

I have been experimenting with Foma 100 since last year and although it works quite well I am not happy with the density of the images compared to other films. I do not have the technical knowledge but think maybe it is not the best film for reversal. I found that rating it at 400 with longer development time gave slightly better results.

I also now think that light reversal may be the way to go. I always thought it seemed a bit vague, uncontrolled and open to inconsistencies but seems to gave the clearest slides.