Thats entirely possible. No need for an island, you make a new settlement in the middle of a big patch of inpenetrable forest. Then when the date arrives, the script (all using console commands) gives a settlement in the east to that faction (The existing factions men are automatically ousted), give that settlement loads of troops, and there you go, a new faction is born. Of course, the faction could never be officially defeated as there would be no way to kill the people in the woodland province.

And another problem would be the one I'm trying to tackle, the fact that loading a game stops the script. I've devised a way of launching a show_me automatically at the start of a campaign, but I've no idea what to do about loading.

In the meantime, the idea for running the show_me script automatically at the start of the campaign worked, but I'm having trouble getting it to start again after a saved game. There are no triggers that I can find which would launch the advisor when you load it.

But there is other good news, the game actually saves the number of turns which have elapsed, so you can save on any turn, and load on any turn, the script will pick up where you left off.