Why are you limiting yourself to steel or carbon? If you want a bike for racing and fooling around then why not aluminium? My next bike could well be an El Mariachi or Cotic Solaris (bit heavier), but not for racing, just purely for fun/winter riding to keep my carbon race bike in tip top condition.
Other than that, looks like a good top quality build, I would shop around a bit in regards to the finishing kit, yes the thomson stuff is top quality, but you can get strong light parts for some right bargains if you shop around.
Also, if you chose the carbon route i'd go with an XT 2x10, or 1x10 setup as I don't think X9 is as good as XT and you're still going to lose the 11speed set up, but then that's personal preference really
And I love the ispec on the shifter and brakes