This is a minor nitpick, but I think it is worth pointing out that when you're talking about differentiating teacher roles and, in particular, how it relates to compensation, you don't really need to pay teachers a higher salary to take on leadership and mentoring roles in most cases. If you're asking them to work more hours, sure, pay them more.
But, for example, to switch one period a day from teaching 25 12-year olds to mentoring one or two grown-ups is probably its own reward. Unless you really don't like mentoring grown-ups, in which case you probably just shouldn't be doing it.
Being a (good) principal is way harder than being a teacher, with heavier responsibilities, but being an experienced teacher participating in the leadership and development of a school is not harder than teaching kids all day uninterrupted. It is, in fact, much better for your mental health and happiness.