[SR-Users] Kamailio as proxy or b2bua?

Hello, My experience has been with Asterisk, but for what I need to do, I think Kamailio may be a better solution. We currently log inbound caller ID information for voip calls (voip app posts call info to a URL). Our users have to fork calls to a custom SIPURI and we log the call information for them. We would like to be able to accommodate users that can't fork calls, and have to register with a provider (PBX or VoIP provider). We see two ways to accomplish this: 1) Act as a b2bua, the user would register with our server and our server would register with their upstream VoIP service (PBX or provider). or 2)Act as a proxy and modify the REGISTER request, such that incoming call signaling traffic goes through our proxy and we forward the signaling traffic on to the user's device. Can Kamailio easily do either of these options? Asterisk realtime doesn't support realtime changes of remote registration information, can Kamailio? Would proxying in such a manner be supported my most voip devices and service providers? -- Eric Chamberlain