If this is true, it looks like BMW's modular engine platform has a working ECU tuning option for the MG1 found in the B48/B58 vehicles and F90 M5. The post from K8 Strasse says it could take as much as 8 hours to flash(first flash), depending on what is being changed. While that is definitely not an optimal situation, at least a bench flash is not required. I suppose a battery charger will be recommended 
Here is a Google Translation:
They have an order page up which directs to their contact information:
B58:
F90 M5 S63:
From today, we are announcing the release of a full-fledged chip-tuning of all modifications of the BMW G-series, as well as the B48 / B58 and BMW M5 F90 engines only in @k8_strasse!!
The process takes place through the diagnostic connector OBDII and takes from 1 to 8 hours depending on the modification of the car, without removing or opening the engine control unit.
With prices and specifications after the tuning you can find on our website, link in the profile.
They have an order page up which directs to their contact information:
B58:
F90 M5 S63: