Would it be possible to implement algorithms with the feedback spread across multiple operators like it is in algorithms 4 and 6 on the DX7? (See the image below; sorry for the large image.) I feel like those algorithms are where the feedback gives you something different than, say, having a saw wave as your modulator.
The current implementation allows only the first operators (with no operator above) to have a feedback. (It's a phase modulation feedback in a frequency modulation synth)
Changing anything regarding the feedback is not on my list.
The firmware is open source and if anyone wants to improve it, i'll help.
I added the feedback to the preenfm3 because many people asked for it, but to my opinion it's 0.01% of the sonic possibility of the preenfm3