this could be related or just 'is' the midi>osc thing but bear with me..
if i had only a single dumb physical midi control (fader or knob) or joystick, and a less-dumb osc device, I'd like to make that one physical control do many things depending on context (from reaper) and change function based on commands from the osc device.
it would be ideal for a portable
'one physical knob/fader/button plus a smartphone scenario'
so some kind of (excuse the non-programmers idiotic take on programming)
SCROLL midi1cc12/scrollwithmymidicontrol
ZOOM_IN midi1cc12/zoomwiththemidicontrol
here 'midi1cc12' is a predefined dumb midi controller e.g
set up as 'control' in reaper, to define the control in question.
reaper, on receipt of /scrollwithmymidicontrol from an OSC device, will scroll when the midi1 cc12 moves, but switch function to 'zoom in' if it receives /zoomwiththemidicontrol from the osc device. reaper will also of course send a string or value back to the osc device to help indicate what midi1cc12 is now controlling. easy peasy right?
to me it seems not really like converting between them rather using osc to define/redefine (and indicate as such) midi assignments.. you get the idea.
feel free to point and laugh, but there it is.