As long as the H rated Diablos are still available and the cost of them doesn't start to become that of super sticky rubber then I am all for keeping them as they work.
I would see no issue with allowing both the H and ZR if that helps to keep the supply up and the prices keen.
Personal preference is to allow wets, but that's just because I am **** in the wet on Diablos so it's purely selfish
although i have tyres warmers etc anyway I can't really see a benefit to them in DD whilst we are sticking with the sensible road tyres that heat up quick. I do think requesting an additional warm up lap would be a good plan, just for the psychological side if nothing else.