I'm currently working on some new code, effectively what could be the new core of RHP, which will play regular orthodox chess, as we have now, and any number of variants. I intend to support as many as possible - currently at about 15, but this should go *way* higher. I’m building for flexibility from day 1, so in theory, they can be added at request.
Once this code is proven, and the plan is to release it on to a variant focused site to do this, then I can work out how to add it to RHP. No time scales on this though! RHP was never built to support variants, and it will be an interesting job to shoe horn them in now. One step at a time.