Crazy? Probably, but I had an old dog of a sail that wouldn't withstand stitching and needed something. I tested some paints on test panels, chose one of the best, and ...
... after 1/2 a season it's still looking good.
This is an inflatable paint I have used before, so I'm not expecting any trouble. It seems to stretch with the cloth and I know it can handle the sun. Would I spec a new sail that way? Undecided.
A full report will be in Practical Sailor next year.