Cyclocross Bikes - SS / Fixed

I've thought about a KM, but the unused braze-ons will bug me. I've basically got an idea of the perfect bike in my head, and am looking to combine 2 or 3 of my current bikes into one tri-purpose build that can switch between wheelsets for different purposes (commuting in shit weather, mtb'ing a few weekends a year, noddy low level CX in winter). But looking around it seems that what I want is too out of line with commercial interests to get anything OTP unfortunately.

This (in terms of the concept) is the closest I've found to what I want, but without going custom I'm clearly going to have to compromise...

On paper a pompino would be ideal, but max tyre is only 700 x 32, which is too skinny for the mtb part of the build.

I don't know really, this is the checklist anyway:

• Either: singlespeed with track ends and V/canti mounts, or geared with vertical dropouts and an EBB (I don't want to be messing around aligning discs in track ends)
  
• Horizontal toptube/easy to shoulder (my bikes have to live in my bedroom, which means carrying them up two flights of stairs twice a day or more)
  
• Geometry suitable for my height (5ft 8" female, wary of a 29er here)
  
• Frame designed to take a rigid fork (if I'm selling two beloved bikes it had better be for a sub-20 lb build)