I started one as well (
https://stash.reaper.fm/v/27173/Notation%20to%20MIDI.zip). I think my version is very flexible, but it is NOT very user friendly. Do we want to put our heads together to try to come up with a solution?
I would love for an articulation mapper to be native to Reaper, but it sounds like it is stalled or scrapped.
Schwa, I think this was mentioned on a pre-release thread, but would it be reasonable to finish the nuts and bolts of the infrastructure and allow users to create a UI via scripting (if such a thing is even feasible based on the infrastructure)?