Having a separate OSC input agent would be worthwile for sure!
In the mean time it could also be a good start to explore the OSC features of Stage. I never tried it but if you load the "direct keys" Stage tab of the midi illuminator it should be possible to directly set the keys via OSC:
/alpha midi light controller 1/keys/key 1 = 1
sets the first key green etc.
Or you could use the direct notes feature via OSC that uses the note to key mapping via layouts:
/alpha midi light controller 1/notes/49: c4 = 2
sets all keys that are associated to the note c4 orange etc.
Make sure that direct notes and direct keys are enabled for the colors you want to set:
/alpha midi light controller 1/green lights/enable direct keys = 1
/alpha midi light controller 1/orange lights/enable direct keys = 1
/alpha midi light controller 1/red lights/enable direct keys = 1
/alpha midi light controller 1/green lights/enable direct notes = 1
/alpha midi light controller 1/orange lights/enable direct notes = 1
/alpha midi light controller 1/red lights/enable direct notes = 1
Then you can decide whether direct notes, direct keys (or midi) should "win" if both approaches try to illuminate the same key:
/alpha midi light controller 1/priorities/direct keys prio = 1
/alpha midi light controller 1/priorities/direct notes prio = 2
/alpha midi light controller 1/priorities/midi prio = 3
would change the priorites from the default midi > direct notes > direct keys to
direct keys > direct notes > midi (prio 1 is the highest priority)
Also took a few days off from "home coding", wanted to know how the novel I was reading ends ;)
Will have a look at file export/import today though.