Problem is the n54 and M3 have the complete ECU inside the ECU box. The tune have access to all the wires.
n55 have harness for each important plugs. It should be easy for BMS or Vishnu to do the O2 sim using directly the O2 sensors plugs as usual (re-route the signal through the JB4/Procede unit).
Here's a pic of those plugs (from Sloppy's thread