Losing Nebraska, ATM, Colorado, and Mizzou definitely hurt. There were no schools good enough to fully replace any of them that made geographic sense. WVU makes sense from the perspective of history, competitiveness, and fire-up fan-base, but not geographically.
As Fearless said, Arkansas could have been a target for a replacement school. And maybe it was. It certainly was the best maybe-possibility. But at the time, the Big 12 looked like it was on life-support (and maybe it still is, although it doesn't feel like it). There was not much with which to tempt the Hogs, who had left the SWC for their own reasons, and some of those reasons perhaps would have still been present. SEC money and prestige were strong inducements for Arkansas to stay put.
Colorado State might have been an option. Maybe 5-10 years earlier, when Sonny Lubick had the Rams really going it would have been a better one.
New Mexico might have been an option. Albuquerque is the biggest city between the line OKC-D/FW-San Antonio and Phoenix. New Mexico is not really a football-crazy state, though.
Once WVU came in, I thought it might be good to invite Cincinnati and Louisville. That way, WVU could have a couple of semi-close (at least in the same time zone) neighbors.
Taking in TCU was an act of desperation.
Somewhere out there, SunDevilFroggy is not happy right now.