A limit to characters.

[juhubert]

Yeah but its still limited to infinity.

well, actually not. it´s just a extraordinary big number ^^

[Pacho]

Until you break out the alt accounts.

[Morgant]

Okay, so. This won't work, to prevent Alt vaults, to prevent murder alts, anything like that.
If a person is going to be a raider, they'll just wait and create a new character every few days. Or they'll create Ten accounts with one character each on it. They know they'll need them, and they'll create more than they need, "Just in case", which worsens the problem even more. (Eating up more space)
What would also happen if there was a time limit on creating new characters, is that "Lawful" characters or such won't have time to say. Create a throwaway alt to check if Raiders are sitting in their village waiting on them, and they also would be able to create new characters to keep their most prized possessions from GETTING stolen.
If anything, this would be better for the griefers.
Just in case you needed most of the obvious reasons this is a bad idea.