I agree on all points - the Big12 still needs a couple more top 15 type football programs to offset what is perceived as an "OU/Texas" league (hell, let's be honest, after the last couple years, an "OU" league).
If you get the four schools that are the most rumored you get everything you could want.
FSU is a top 15 program which gives Texas and OU another major opponent.
Clemson is a solid addition, on the lines of a rising Oklahoma State.
Louisville wants in the Big 12 and would give West Virginia a nearby rival.
Georgia Tech can be competitive, but what they bring most is academic cred (which got hurt when A&M bolted).