The forums I am on or have been that have regional chapters (LX Forums, Grand Prix forums come to mind) generally have thousands of active forum users (paid or otherwise). The way they handle regional groups and subforums is different. ClubGP.com, for example, sets up additional domains, which costs money, whereas LXForums.com has subforums titled for the local clubs (Frozen North LX Club, for example)... Modern Mopar groups usually have their own domains or choose social media to create the group, where PAMMG (Pennsylvania Modern Mopar Group) has a domain and forum and DAMM (Detroit Area Modern Mopar) uses a Facebook group. AFAIK there isn't an all-encompassing Modern Mopar group. Each group is created only when there are enough active people to justify its creation. Usually dozens are required. When there aren't enough to create a new regional chapter, they're lumped into an existing neighboring chapter. Jersey Shore Club GP (JSCGP) had dozens of active members, however the admins of ClubGP lumped us all into the Mid-Atlantic Club GP chapter. We had (or have, I haven't been there since 2010) our own domain supported by paid members.
That said, if there is interest in creating subforums for regions, then it is something the BOD can discuss internally. My recommendation is to handle it the way I've seen ClubGP and LXForums handle it, on a case by case basis if there are enough interested people to support the creation of a regional forum for a particular region. Currently, I am not aware of any interest beyond this thread.
2002 Chrysler 300M Special - Deep Sapphire Blue/Storm Gray Metallic - 142,000 miles