When I looked at the idea of the Magician's Isle in TME, and thought of how I'd do it, my immediate thought was to do it with a Mercurian cult and a magus Ascended to Daimonhood. A Titan-level Presence across the isle will be a giant LOL NOPE sign to the faeries (though beware; some powerful faeries might be encouraged to invade in hopes of a Titanomachy), as well as creating a Magic Aura of 5 across the isle. That means that a local church will not have a Dominion Aura except in the nave and on holy days. (Pick a rock in a spot of great natural beauty to start from, and engineer your temple-covenant around it, for even better aura there.)
Of course, to do this, you need to start with an ancient magus.