[Closed] Is this future build doopid?

Ok so I wanna build a cyclocross;

Single speed, fixed gear and SPD with discs

I was thinking about buying a Cotic roadrat but I'm thinking the BB clearance won't be enough, because being a fixed gear the cranks'll be constantly spinning and might hit a rock on a tight turn or something.
Then I thought about a fixed gear frame, so it has high BB clearance but they have V brake mounts or no mounts...
Also the roadrat might have to force the dropouts slightly closer together...
Help Please

Any frame recommendations

Thanks,

Mike.