Sure that can prevent people from bypassing the limit easilly but it affects certain groups of players more than others. College players may be unable to log in because there are others at their university who play. People who use public wi-fi will be unable to log in if someone else is on their network. People in a business will be unable to play during leisure if someone else plays. Those who live in the same household will be unable to play together. All of this can be bypassed by those who want to take the time (similar to how they evaded bans in RoK).I suggest you use another method. The easiest would be to simply have the client create a unique ID based on a computer identifier (MAC address or something) and that would limit the connections to one player per computer. While this too can be abused by someone with multiple computers, it will solve the problems for people using public or shared connections. I think you need to maximize the access players have to the game. If you come out in the future with a web client the IP lock feature will prevent the game from growing.
I'd think on changing this if I were you. Client side authentication is not perfect but it also takes some skill to bypass. IP locking is fairly easy to bypass but takes knowledge and a little effort. Wieght the pros and cons of each method and see which works out best for you.
