Interesting aside. I used to run a 1x6 drivetrain with 6 cogs of a 9 speed cassette installed on a Hope singlespeed hub. Gave zero dish for the rear wheel, which was pretty cool. Although I don't run that drivetrain anymore, I still have the wheel, and I tested it out. With the XTR 11 speed cassette, I can get 8 cogs on the singlespeed hub. The only problem is that in order to use a lockring I would have to modify _something_, but I thought that was interesting. When I started MTB'ing it was 7 speed cassettes - and I could now run an 8 speed cassette with zero dish in the rear.
Only problem is I don't think they offer a 142x12 conversion for my older hub.