looks like 2019 is FM year:
"XFM is a polyphonic, 32-voice, 6-operator FM synthesizer stereo module that you can build yourself.”
its based on a cheap FPGA chip and clocks in at less than 100$.
i exchange several emails with the (very friendly and responsive) developer, who told me, that he had an architecture similar to the tx816 in mind.
since the hardware has already midi link built in, that should be very straigthforward.
i suggested loopable envelopes and a pitch eg per operator and he replied that "the "inexpensive synth challenge" has been cleared”, he is working on a project with a more powerful FPGA board, which *could* host these things and other ideas too.
definately on my watchlist!
cheers
hans