Hmm, sounds to me like you want to re-create
pfSense (a FreeBSD-based firewall distro that uses pf and provides a nice web-based admin tool). You'd be better off giving that a try, and seeing if it does everything you want. I'm guessing it will.
And if it doesnt, you can always hack it to add what you need, and maybe they'll accept the patches to make it available for everyone.