so you haven't tried adv's yet? worth giving it a shot before you make some more drastic decisions...
Edit: I just found a post from jul 25th 2018 saying it should be soon. You actually posted in it about buying a syvecs. We aint ever getting downpipe o2 for mhd

yeah its been going on for a while. there were also an old thread were I had a
feeling the dme needed the sensors to be the correct distance away from the exhaust ports as well, and I've since found out that is the case, you can read about it here;
https://bimmerprofs.com/tests-chemical-efficiency/
So you use syvecs if i read correctly?
yes.
so with a standalone you will have a map that tells the ecu how long in milliseconds the O2 reading is lagging the combustion event otherwise the closed loop operation can go into unstable oscillations. however bmw takes it one step further and uses the twin sensor setup to make very fast cylinder balancing calculations and adjustments as per the article. if you understand that article, you might understand the complications that might ensue trying to run single bank 02 if not all the necessary tables are found.
you might also wonder then, since piezo injectors are so sensitive and open for such short periods of time, if the control system isn't so elaborate am I leaving myself exposed to a greater mismatch in flow to cylinders with only a single bank reading (relative to controlling conventional injectors). just food for thought, and gets the thread somewhat back on track!