Be warned, this is fluff:

A notify field when you start a thread (or post) where you can enter 2-3 usernames that become notified of the thread or post (via pm, email, w/e)

If perhaps, someone creates a thread spawning from a previous discussion where some members are actively involved, they might want to be notified of the continued discussions existence. Obviously the PM or AP system can be used for this, but it may be more convinient. Or for instance if a member reads a thread and knows of another member that may be interested (suggest a thread).

Just something to think about. If it flys, make sure it's designed to handle abuse.