Is there a tool..

[Cheeder]

Or an add-on which would allow more than 12 people to connect to a game?

I think WOWIII is implementing such a thing. I don't know how they are going to do that but it would be nice if such a technology was shared.

 

[Shadow_Fox]

Check out project forums "Reinventing the craft" One of its main goals is to allow the player limit to be extended through the LAN, as well as add keyboard detection and other neat tools, read more about it at its Project Forum