I do wonder if the devs might regret introuducing the Island Sanctuary. It looks like they had resources that could have been used for instanced houses and chose to use them for the Sanctuary instead. I certainly can't accept the 'instanced houses are impossible due to limited resources' argument any more. Though in fairness, it's usually people here forwarding that argument and as far as I know, there has been no official statement to that effect.
Even if it is far more limited than a house, the fact that the Island Sanctuary is available to each character, suggests a lot of resources have been devoted to it.