A few things:
1) Yes my name is a reference to Doctor who, I haven't watched much since the very start of the Capaldi era though. I don't know if you've watched old who, or if you're just watching new who, but you definitely should if you haven't. Many of my favourite episodes have come from old who, due to the laughable effects and higher-quality writing.
2) I agree that
Island Sanctuary is fine. While I do think that
Island Sanctuary as a card does shut down aggro pretty hard, I realise that's not necessarily a bad thing in a format which would undoubtedly be dominated by aggressive decks. Forcing these decks to start running green and/or white to deal with the sanctuary would likely be healthy for the format as a whole.
3) I totally disagree with the assertion that
Mana Vault is okay because any deck could run it. Starting the game with 3 extra mana means you're almost guaranteed to win. I built a goblin deck for coremat which would essentially win the game without contest if it was able to start of the game playing Goblins like
Goblin Rabblemaster,
Krenko, Mob Boss, and
Siege-Gang commander and the opponent was unable to make similar plays. And that's not exactly a deck designed with
mana vault in mind.
Mana vault for this format could be equated to
Black Lotus in vintage or
Sol Ring in commander, where every deck is forced to play it and each player hopes they draw theirs and their opponent does not for an easy win.
4) Totally unrelated to Red_Wyrm's post, but looking at the format top down, I think
lightning bolt might just be too powerful and would allow aggressive decks to
dominate the format. Control in the format isn't quite good enough to compete with the ridiculous potential of burn and aggro decks, mainly because of
lightning bolt. The power provided by this one card would likely shape the entire format around aggro, with every strategy (e.g. midrange, combo) being unplayable unless relegated to either aggro or anti-aggro because of the damage this one card provides.
Obviously, the best course of action would be to have most cards unbanned and see how the format would settle before making any bans beyond the first few, but a few bans have to be in place from the start due to their clear and undeniable power. (e.g.
Dark Ritual,
Necropotence,
Mana Vault,
Vampiric Tutor,
Stasis)
EDIT: I AM AN IDIOT. I made most of these judgements prior to looking through M10-M20. Now that I have, I realise that WotC has done a good job in recent years of making control viable in core sets.
Lightning bolt and aggro in general are not as powerful as I considered them to be earlier. Ignore my comment regarding the bolt.