I'm going in this direction too...
I already have a RO/DI unit, automated water changes / fertilizers / additives, and eventually I want to keep discus. So I will use RO water and keep a low PH and KH, and aim for 5 GH.
But I wonder abou 0 KH... Common saying is that some KH is necessary to keep pH stable. But I'm reading more and more about people who keep 0 KH and it works well.
So it's the only thinkg I'm not sure about. Should I add something to get my KH to 2? Or keep it at 0?
I'll probably try it with 0 KH, I think stability is the key there, and with everything automated it should be stable enough.