I’ve thought about this some myself, and decided the best thing is Pigments itself. Start with one of those small but powerful Windows computers using it entirely dedicated to running Pigments in standalone mode. It would boot into Pigments. Then combine that with some carefully crafted controls to minimize the mouse sort of interface.
One option that i’ve considered is the MP Midi Controller.
This isn’t perfect, and it isn’t cheap either, but it goes some ways towards the Pigments Synth.
What i have done instead is wait for Arturia to do the real thing.