You could add 2 gallons or so of e85. That will boost your octane. Here is a link to help you calculate:
https://www.brewcity**********/about...ol-calculator/
Most stock tunes will allow for 87 as the lowest. This is incase it is accidentally added to the car. Adding e85 (just a couple gallons) will significantly boost octane (e85=100 to 105 octane). Just remember it has a lower ignition temp (good for the motor), but it will burn about 30% faster. For this reason, dont add too much, unless you tune for it.
Im in a super charged e92 m3 and mix every now and then. Generally its advised not to mix more than e20. The f12 m6 has a better fuel system, so you may able to do more.
Running the 87aki will slow down timing quite a bit. But the stock config will allow it, its just not good. All bmws love octane
Good luck! Also I should be getting an f12 m6 and building it in the near future. Hopefully will keep the m3 for the track and m6 for daily.