Unfortunately the perceived brutality of kicks and stomps in general due to these specific uses will be what keeps them out of north American MMA.

I used to argue for allowing stomps in the cage, until I saw Mir vs Sims and then listened to some discussion about the dangers in a cage as compared to a ring. I'd still like to see them allowed on a trial basis.

I still think kicks and knees to the head of a downed opponent need to be allowed. They are no less brutal than elbows to the head of a downed opponent (which promotions like Strikeforce don't allow). Also, at a minimum kicks to the head when performed as an upkick should be allowed.