southpaw,
I completely understand where you're coming from. I think many pitchers with significant experience from working with Tom House and/or coaches trained by House would prefer to remain associated with him and his methods.
But TPM makes a number of excellent points, all of which are in agreement with House's own philosophy.
First priority is the education your son will get, not the baseball program.
Second, there are many outstanding pitching coaches who are not associated with House or the NPA. Jargon may differ, and specific drills and approaches to certain issues may differ; however, you can absolutely find great pitching coaches who have independently developed their individual approaches to pitcher training along very similar lines to the NPA protocols. There is a lot of cross-fertilization in baseball. The smart guys learn from everybody, keep what works, discard what doesn't work, and they evolve and adapt as they go. I think Tom House does a terrific job of this--certainly the best I've seen, in my opinion. But even from my limited experience, I've seen other coaches whom I respect deeply and whose approach to teaching pitching meets all of my litmus tests.
Finally, one of Tom's central tenets is, "Every pitcher should eventually strive to become his own best pitching coach". That obviously doesn't mean that pitchers develop to the point where they don't need coaching from others--it means that they should develop a strong sense of self-confidence in their own abilities and self-knowledge, both strengths and weaknesses.
I don't think most pitching coaches at higher levels of baseball spend a lot of time fixing what isn't broken. If your son has a solid mechanical foundation, has learned conditioning routines that work, and simply needs to keep developing his strengths...I'm guessing that most coaches would be extremely happy with that. I'm sure some coaches are the 'wrong fit' for certain pitchers, and 'horror stories' are always easier to remember than the completely satisfactory outcomes, however, I'd guess that you can usually sort out the ones who clearly would be a 'wrong fit' before making a commitment--that's what diligence visits are for.