I do cringe occasionally when I see those soccer kicks or stomps landing, as brutal as it looks I still think it was a relatively safe aspect of the sport, even if it was the least safest.
I don't know if the UFC needs them. I'm not really jonesing to see soccer kicks and stomps, but I wouldn't be complaining if they were added (which they won't be).
Knees to a downed opponent on the other hand, I really would love to see. Adding that would add so many new elements of strategy to a fight. I think I might even be willing to trade elbows for them. Now don't get me wrong, I love elbows, but I hate the fact that they cut fighters so often, even ending the fight if it's bad enough.