I've read your article about Kamailio as an SBC and found uac module description with uac_restore_from() and uac_restore_to(). It looks like suitable for me, so I'll try to use it.
uac_restore_from() and uac_restore_to() works fine, but next I need to modify ip address in SDP headers in responce - so it will be more suitable to use SEMS or FreeSWITCH.