Cool!
I've looked at the Nashville system no telling how many times. I suppose once you get it it's easier. To me it's less work to just go find the chords in the right key. However, when you can't get that, I can see where it would be helpful. Otherwise it seems like more work than printing or having the correct chord chart. I'm possibly missing something. If I were needing to constantly change keys I would buy one of fancy quantum physics boxes that changes the universe so it sounds like you're playing in another key.
