VTOL Duo Tailsitter: actuators (motors) on AUX port, possible?

To maintain compatibility with other AP systems I would like to be able to use this actuator mapping in my non-vectored tailsitter, if possible:

MAIN5: elevon left
MAIN6: elevon right
AUX1: motor left
AUX2: motor right

I’m trying to understand how to do it but I do not find exhaustive documentation about it (if is possible, obviously without putting my hands to the code.).
All work fine here with the standard common output, so:

MAIN1: motor right
MAIN2: motor left
MAIN5: elevon right
MAIN6: elevon left