BTW what about using a standard sequencer but routing the results through scaling and transposition?
Modules: vermona Amplinuator would give you scaling including over 1x, "AJH synth precision voltages" would give transposition.
From the Ideas described in video above I think this might give you a solution in modular. Might be a pain to calibrate or dial in initially. But IMO this could work!? This is a potential solution only for the tuning side of the problem; what remains is the OSC to get a suitable timbre. That said, I would think the complex OSCs with FM (or any good FM implementation) would give you good options for getting inharmonic yet tracking partials.
I've been thinking about how to use my sequencers for stuff other than pitch control; routing them through attenuverter with offset is a good option for me to try. Made me think again of this thread.
Please let us know if you have progress on your effort. Good luck!