some ideas here are not good here
1) one account one ISP ip - I am playing with my wife and my kids from a lan connected via a router to my ISP ... same ips visible from outsid
2) simulan casting - with some tools you can programm easy some random delays ...

the main reason for blizz is that all accounts have to be paid. And I guess that the most character transfers between accounts are made by multi box players.

BR

AwA