not much to add to what @desolationjones said. basically, it would be similar to using faderbank with teletype - without TT you run it in leader mode, so it pushes changes to ER-301, with TT it has to be in follower mode, and then you can use metro script to poll for values and push them to ER-301.
in terms of dedicated TT ops - i think in general it’s best to have dedicated ops for each device, but this sounds like a pretty special case, and it would be easy to re-use fader ops for it, especially since we allow up to 4 faderbanks on the same i2c bus.
a better option to consider might be adding new device agnostic ops for controllers (since it’s likely there will be even more devices supporting the i2c protocol). something like CTRL or similar. these could support any number of values (instead of being limited to 16 for faderbank) and we could allocate address space for up to 8 devices.
curious, is hardware mod required for it, or is it just the firmware?
edit: let’s split this into a separate thread.