I don't have a lot of detail for you in this post but I can tell you for sure that it's possible to use Kamailio as the SBC in front of Freeswitch, with Kamailio forwarding the SIP registrations to FS. I currently manage a system with that architecture which has been in production for the last 7 years. If you need more detail, ask questions as specific as you're able. I have some time on my hands over the coming days and I'm willing to help.
I don't have a lot of detail for you in this post but I can tell you for sure that it's possible to use Kamailio as the SBC in front of Freeswitch, with Kamailio forwarding the SIP registrations to FS. I currently manage a system with that architecture which has been in production for the last 7 years. If you need more detail, ask questions as specific as you're able. I have some time on my hands over the coming days and I'm willing to help.