I don't know if this is possible, but it'd be fantastic to be able to change the visible F key names. I can already change their function with Keyboard Maestro.
That would give a whole new row of functions to the Touch Bar using the fn key, and make it much easier to remember what they are set to do.
I'm envisioning having my BTT buttons visible normally, and when I press fn, instead of F1, F2, etc. I see names I can choose. Only the visible names have to be changed.