[sr-dev] how to make non compliant and custom SIP implementation works with Kamailio

Hello, I have Aastra phone that doesn't seems to get new firmware and most importantly NEC Hybrid IP phones. My question is, how can I "adjust" Kamailio to get these phones behave like SIP compliant phone. Which kind of Module do I have to develop? For the NEC story, I will actually dedicate a separate Kamailio instance if some workaround is possible. Someone offer me a complete NEC system to do this: NEC phone system + plus some NEC IP Phones for the "reverse engineering" task. So I will be able to see all the SIP traffic on the NEC system and will adjust Kamailio to handle them. Possible??? Thanks, Vic