First of all - I have good skills in OpenBSD. We use it here at my work to firewall our network, and I've used it at home for the same purpose for the past 2 years. FreeBSD is quite similar to OpenBSD. FreeBSD can use either of 3 firewall systems - PF (which is the one used by OpenBSD); IPF; and IPFW. All 3 of these have similar syntax, so if you're not using PF, I'm confident that I could sort it out from my knowledge of PF.
I should mention that, amongst other things, I am the person in my work organisation who is primarily responsible for IT security. I work in a team of 25 IT professionals, for an organisation of 1200 staff.
On top of that, I have been a Unix sysadmin since 1993, and Linux since 1999. I've administered FreeBSD in the past, but not since about 2001.
On the web development side, I don't have experience with Cpanel, other than as a user :-). I do however have considerable experience with Perl CGI development. Amongst other things, I am the author of a Perl CGI application that is part of the Mandrake/Mandriva Linux distribution. I've had a quick look at the links that you listed re. Cpanel development, and it looks fairly straight-forward (I don't think that Cpanel integration will be a major component of the work for this job).
I think that most of what you want should be fairly achievable, however I have one comment to make - it would be very difficult to block connections based on country. Firewalls are IP-based, whereas country information is, at best, DNS-based. I can't think of any way of configuring a FreeBSD firewall to reject connections from a particular country, without making some major changes to the source code of the firewall, probably even re-writing it.
All the best
mjtg.