After doing a quick search, I haven't seen this mentioned...
Maybe I missed it and it's hiding somewhere deeply, but I'd like to see the ability to 'name' note lanes. We see Kong do this automagically, for instance, but if setting up a drum kit in NNXT, we just get a piano roll, or if using the drum view, "Note #xx"
What I would like to see is being able to double-click on that "Note #xx" and type in a better mnemonic. This feature could be added to the existing menus:
In the example pic above, I've also allowed for colour changing of lanes, but that's icing on the cake. ^^
The files could be saved as txt or xml files in a folder in the Reason directory (by default), making them accessible across projects. This would minimize coding, I believe, as you wouldn't have to add anything the the NNXT (for example) to make this work.
For a cherry on top, this could even be expanded to graphics:
Though, admittedly, I can only see this being useful in a microtonal context. ^^