Thanks for the insight!
Honestly, I'm having a really hard time to get it done. everytime that I try to configure this function I'm getting a parse error. I've tried "rtpengine_subscribe_request" as document in both kamailio and rtpengine sipwise documentation, but I find it weird that in the kamailio/src/modules/rtpengine the rtpengine_subscribe_request is not being exported, but rather a rtpengine_subscribe_offer. How did you manage to get this working?