First, this is at best a devloping area of study and application; it is not well developed at this point.
Second, it’s not clear there is adequate demand for the area; the person may end up being unable to find a school job or a university position in this area.
Third, many of us feel that yuou have to know some model-based system dynamics to teach systems thinking well, and this person’s study plan does not mention studying to become a good modeler so as to become a great systems thinker.
Fourth, which maybe should have been third, there are a lot of characterizations of “systems thinking” which can be very different. I assumed the person was interested in “system dynamics thinking”, but that may not be true. If not, then I’m
not the one to try to help.
A better PhD plan would be to get the (research) degree in a widely recognized field (system dynamics?, cybernetics?, human cognitive development?, education?, critical thinking??). Become expert. Get a research/teaching position at a university
(that’s the only reason to through the pain of getting a PhD). Then try applying it in schools, preferably with people who have been trying to do that for quite a while now.
Sorry to be pessimistic. Trying to be realistic often heads me pessimistic directions. Certainly, heading for a PhD should involve a lot of realistic thinking about what one has when done. Is it worth the journey?