If CU joined the Big 12 with UA, ASU and Utah... and they went division-less with 3 paired rivals we played every year (the current scheduling trend, which 3 Big 12 teams would we want?
My hope is that we'd have enough leverage to dictate a bit and get a TX team or two. TCU, UH, UCF and Cincy would be the best for recruiting if that's our focus - even though there's almost no history. If the focus is fan passion and attendance (including road trips from CU fans), maybe KSU, OSU, ASU and Utah?
NU, OU, and MU.