I wonder if this could be implemented using apps like Keyboard Maestro too? Since most (all?) Sublime features can be keyboard bound, so if not Sublime will offer it, maybe keyboard helper apps will?
EDIT: "The API for the Touch Bar does not appear to allow non-front applications to affect the Touch Bar, except that Apple does this themselves in Xcode and Screen Capture and the like. So Apple knows and understands the need, but have not made the facility available for Third Party macro trigger style applications."
So I guess we're left to hope that Sublime can integrate it then