I just did a partial mechanical dissasembly this weekend and checked everything out. I will have to repin my connectors but the wiring harness appears to be fine. I'll also need to figure out what to do with the parking lock pins....this is the big difference between the 335is and M3 GWS shifters. The 335is has a "park" switch that engages the park selector. The M3 GWS doesn't have this and the TCU simply engages park when the engine is turned off. I'm assuming I'll just need to leave these pins unused after the swap. Other than that there was one other small blue 2 pin connector that I'm researching as it exists on the 335is GWS but not the M3 GWS. Not sure what that is either.
The sport button and drivelogic button appear to be a simple swap, and the Power/EDC/DSC buttons are superfluous to everything other than launch control. So that will be phase 2 for me. I did order a cheap CAN sniffer to sniff the PT-CAN BUS to see what exactly is the PT-CAN messages that trigger launch control for both the 335is and the M3.
@Terry@BMS didn't dismiss me when I asked if the JB4 could emulate these CAN signals to force launch control. I think he may be willing to test if we can provide the address and payload of the requisite PT-CAN messages. That would likely be the fastest and cheapest solution to adjustable launch control. Nothing against
@jyamona or MHD, I'm sure they can do this too, but their plates are REALLY full right now. And the obvious final solution is Syvecs for a cool $5k.
Just to recap, it looks like we can have full M3 drive logic with a fairly simple swap of GWS, DriveLogic button, and Gauge Cluster then flashing the M3 TCU ZB files over. The Launch Control won't work however at all in this setup. We would need to emulate the PT-CAN signals to turn it on (this is how Syvecs does it, they did disclose that).