What about this as a possible way to stop a great deal of this problem? Only allow verified accounts to play from devices that show the same Local IP address every time they log in to play?
If a player changes residence and, thus, their IP changes, a simple re-verification would be all that is needed. Continuing along these lines, would it be easier to verify accounts using player's ISP & IP's. as opposed to bills and other more personal information?
This way, a simple program could just keep them from playing at all if they log in from a different ISP or IP. The game can't be played very well, at high level's, on iPad mini's etc. anyway, so only need to use a phone or pad to play on is if it's the only way for a person to access the site.
Like other suggestions. only a thought.