So far, I quite like the Sanctuary hub. It's a neat little area that fits within the Fable
world's lore and I like the details that go into making it a real place. I'm early in the game, so it's not very large yet (you unlock areas - clothes, weapons, etc. - as you progress) but I think referring to it as a "mansion" in any sense will give an exaggerated sense of its likely full scale. My only small complaint with the Sanctuary so far is that it does feel a little cumbersome to have to go there to save once the Sanctuary is accessible. Until you uncover the Sanctuary, you can save through a traditional menu but once you have access to the hub, the Start button will always take you there, where one of the options in the first room is the Options menu that allows you to Save. Other than that one minor issue, I don't think the hub is unnecessarily complicated; I do think it adds to the immersion. Plus your John Cleese-voiced butler Jasper is there, so that's enough for me!