I did a bit of a research into this because the BT controller is pain in the ass.
The cheapest way to do this is to source couple of actuators from any non-M BMW (actually the stock OG M2 without MPE also uses that part number).
You replace the MPE actuators with those, add a Y connector (OEM part for some M performance model), and plug it into a connector that was disconnected during the MPE install.
Total cost would be $200-$300 depending on where you get the actuators.
Here is one of the threads where we talked about it -
https://f87.bimmerpost.com/forums/sh...ght=mpe+wiring