1. Do you feel experience requirements are acceptable in Large (Theme/Normal) games?
Yes. I am of the opinion that who is let into a game should be at the sole discretion of the mod. There are plenty of other games to join if a given mod doesn't want you.
2. If so, do you think they would be appropriate for other types of games, such as Mini Theme games?
Yes. Discretion of the mod. I don't see how that would change just because the game got smaller.
3. Should Mods be allowed to ban specific players from their games?
Yes. A mods game is their kingdom. Just as they should be allowed to modkill and set rules at their discretion, they should be able to oversee the signups at their discretion.
4. If so, what reasons are acceptable for doing so?
Anything. What the mod decides for their game should be law. If a mod wants to ban all players with a name begining in "R" from their game, then they should have that right. It may be a bit stupid, but so are a lot of things that happen in a game of mafia. My main point is that the mod should be the sole determining factor of who plays in their game, and in what capacity.