Well most of those E46s here in the US had traction control and stability control. Since the network can't interface with your GM ECM you might be able to recode the other modules to either not see the ABS module or have just plain ABS without traction control. Thereby getting rid of the nasty yellow traction control light on the dash.
If you could find an E46 with just ABS you could use that hydraulic unit with module and recode the car. You must find a good BMW tech or Google to your hearts content.
This is the main reason people shy away from newer engine swaps. With todays technology sooner or later someone will reverse engineer networks enough to rewrite some language to use the GM ECM with whatever platform you are sticking it in.
I am a Volkswagen/Audi tech. On those cars one can simply pull power to the module not wanted (such as ABS) and simply recode the CAN gateway module (the module that looks for all the other modules) and a few others too so the car will function withoput all those lights on the dash.
Anyway not bashing you or your work because you my friend are a trendsetter. You have done something very few have accomplished. You took an already nice ride and made it VERY nice and now FUN to drive!
Regards, John