unSpawn's right, your firewall should be designed in such a way that users shouldn't have access to modify it.
Now on the other hand if you have an admin that needs access then the best solution for you is to use this:
It's a GUI with SSL login for admins.
Basically it's a very comprehensive GUI that uses IPTABLES as it's firewall. "They don't tell you this but the output from the logs in the demo looks like iptables output"
I suggest your check out the online demo and decide for yourself.