If you feel up for it, a combination of ideas might be your best bet. Idea #5 might be good, too, but it's probably not good to just stop midstream if you're already motivated and working on it regularly. Maybe finish that one up and also work on one of the other ideas for NaNo?

My NaNo this year (as far as I have planned), is sort of the equivalent of your Chatoyant College in that it's a world I've written a few books in over the course of several years. There's something appealing about minimal worldbuilding and already being familiar with the characters, but I'm like you--I'm afraid I'll get bored. I'll also be a NaNo rebel since the book I want to work on is already started. But barring my having any dazzling new ideas before November 1st, that one's probably my best bet.