That's too much risk - what you guys want to use is pfsense!!! its much less risk and much much easyier to set up ... and it works for a big mass of clients if you use god hardware.

check it out:

http://pfsense.org/

                 or:

http://m0n0.ch

http://forum.pfsense.org

^^ those are the very best to do stuff like that !!!

regards,

LeoLinux