People who know Nashville system are gonna struggle with that.

Am I understanding correctly that it always starts on C (C==0)? Seems like key changes will be hard without computer assistance, I mean, you could have your chart update on the fly if you're using a tablet, but paper charts will be hard to transpose on the fly.

I do think now is a prime opportunity to get away from traditional notation for folks that want it, since transcription to a new notation is trivial now, even for paper charts, where it once required a lot of human effort. And, isomorphic is very appealing.

But, this feels like it doesn't come from the perspective of a musician who plays from charts? Musicians think in relationships, not absolute notes, and this kind of obscures those relationships. I'm not really arguing that traditional notation is optimal, it takes a lot of knowledge and practice, and I've never invested enough time to be good at it, but I don't think this really resolves the pain (you still have to know traditional notation to be able to read it) and adds something that isn't based on musical relationships and maybe even makes those relationships harder to see for a trained musician. To a musician the numbers they know are scale intervals; a "7" here is a "5" (perfect fifth) to a trained musician and a "4" is a "3" (major third), but only in the key of C, otherwise it's not a relationship you can memorize, you gotta do math.

It's fun to tinker, of course, and I'm not trying to shit on your idea. Just pointing out why I wouldn't find it helpful. As a musician, who isn't all that great at reading traditional music notation, I find the numbers distracting. It adds to an already noisy and difficult to read thing, one more thing my brain is trying to translate into something my fingers know how to do.