Couldn't you wire folding mirrors from the mirror control switch ? In case of a heated mirrors, they are powered from the same yellow/black which powers mirrors control switch.
Yeah so back to the topic, drilling was not required for me, i just wanted to fix somebody's terrible job. If i would have known how to open the connector, i wouldn't needed to solder 18 wires

After every solder, i inspected everything from different angles and all was looking mint.