I'm pretty sure that many would join an Extinction based clan. You have to remember this is Extinction's debut, and I doubt that IW was ready for the fact that it would take off so well as it did. I'm sure there will be much more planned for it going into the future titles etc. They may even expand their clan competitions to have something specifically branched into Extinction.
However, with all of that said, I think it's a great idea and that you would have plenty that want to join up. Give it a try and let us all know how it works out. If requirements aren't too strict I would even join.