Another thing about the water down talent with too many teams can impact a pitcher. You have a talented pitcher who doesn't have the defense behind him he can lose confidence, throw too many pitchers when routine grounders and flys are misplayed, and start trying to strike everyone out, which can set back development.
I am partial to the Merrimack system having worked there and when I found out that Tommy Hudon who was an outstanding freshmen this year would be playing 14U ball this summer instead of Legion I was a bit dissapointed. I don't see the benefit to him to be playing against 8th graders all summer both offensively for the pitching he will face or as a pitcher.