The VIP thing sounds clever but I'm not sure what advantages you can give people apart from more money and spawning abilities, which I wouldn't agree with giving as it hurts the economy/sellers.
All I can think of is a different colored name (a VIP club house would be too exclusionary from the other players since the reason we're online in the same world is to sort of socialize), but eventually it would only be new people who had normal color names and we'd just have a 'too many chiefs and not enough indians' regime.
Perhaps give VIPs the ability to activate the mob arena mini game when you get it working.
edit- or perhaps VIP could activate a dig game, a hole with one huge block of dirt, stone, sandstone, or wood in it (the VIP chooses which material, sand and gravel too dangerous though), then everyone who joins the game competes in the dig to find the special item, could be a block of diamond or gold or something else good, hidden among the material, but the VIP can only activate it once every 2 hours or something, and the players have to pay to join, so it doesn't hurt the economy too much, if that kind of game is possible (use a specially permitted world edit command/feature to import a premade block, but then there'd have to be many different ones so that the special item is in a different place each time). There would need to be a thing that takes back the dug resources after the game, I think that's fair. (warps and similar commands would need to be disabled to prevent item storing too).
