I'd love to see Twilight Sky get back on staff, just to watch him do a better job than he did back then. I wasn't around when he was a mod, but I've asked a hell of a lot of people about it, and I reckon he'd do a better job this time around.
Ryoutarou seemed like a pretty cool cat for an admin, judging by his old posts. Plus, I picture his username looking better in red than in the default forum colours.
Shiny Umbreon, because he was flipping awesome and his username looked awesome in blue.
Wakachamo, if only to see what he mods like.
There's probably more, but I'm too tired to think about it right now.