As a former football player, who used to play defense a bit, this is what I think about banning the hip-drop tackle.
Okay, fine, ban it.
In exchange, defensive holding shouldn't be an automatic first down. It should just be a five yard penalty. If it's second and twenty, it becomes second and fifteen if there's defensive holding.
In fact, get rid of all of the automatic first down penalties against the defense unless you meet them with automatic fourth down penalties against the offense.
How's that sound?