[SR-Users] Any substitute or replace function for the request-/response line of SIP messages available?

Hi, I have a very specific situation that the implementation of a customer SIP user agent is absolutely not standards conform. Therefore, I use Kamailio as a SIP protocol adapter between the non-standard conform user agent(s) and the typical RFC3261 compliant user agents. Most conversions are working fine. But in a very specific scenario I have to change/convert a SIP response message to a SIP request message and change the SIP method´s name. This conversion is no problem for the SIP header fields. However, I haven't found a way for adapting the response-/request line of a SIP message. This line seems to be protected. The described situation of the perverse conversion I try to realize is following (please do not ask "why?" or think I'm mad...): (mad) UA1 == INVITE ==> SIP-Prot-Adapter(Kamailio) == INVITE ==> (typ.)UA2 UA1 <== BYE == SIP-Prot-Adapter(Kamailio) <== 488 == (typ.)UA2 UA1 == BYE ==> SIP-Prot-Adapter(Kamailio) == ACK ==> (typ.)UA2 I use the "textops" module for substitution and/or replacement in SIP header fields. But the "subst" and "replace" functions cannot be used for the request-/response line on top of the SIP messages. I was a little bit irritated, as the "search" function is still working on these lines, but not the subst/replace function. Creating a new SIP message with the UAC module (as alternative) is not okay, as this new message does not use the same values for Call-ID, From-tag a.s.o. and these values can't be changed before sending the message. Does anybody know a way / function / method for manipulating the request-/response line of a message? It would be perfect using a function á la "sed"/subst. Thanks Klaus P.S. I tested with kamailio-3.3.3