I would recommend that before you jump the gun on what regions need new regionals, maybe focus on what areas don't already have them that could use them more.
Boston has already been mentioned, and I can see that there are so many teams in that one area, despite nearby regionals, there is nothing in state. Good idea to fix.
However, geographically, what areas are developing right now in each region that really need the consideration of a new regional, and need suggestions? I don't pretend to be the most informed about it, but look at Wisconsin...
Anybody got suggestions in Milwaukee for something great? From what I hear, that state not only has some extremely awesome teams arleady, but has at least 8 or 9 rookies in the works for next year. I'd definitly want to see a regional location up there. Feel free to check out the thread about the possible regional as well.