You can absolutely discipline a child without resorting to hitting. So in a sense the policy should have no drawbacks.
I'll tell you what does bother me a bit though: just about every argument which is used against corporal punishment could potentiall be used against almost every other form of discipline as well.
And what worries me is this: that it can represent the starting point of a process by which all forms of sanction levied against children start, one by one, to be classified as abusive.
Look at Sweden, for example. It led the way in banning CP first in schools (actually, I don't think it was technically the first country to do so, but was one of the first), and then in homes.
But over the decades, it seems that other forms of discipline and punishment have also become taboo in Sweden--with the spread of ideas that it is cruel to raise your voice to children, to remove privileges, to make them do time-outs or detentions or what have you. One of the reason why Sweden and Norway have seen their educational results sink steadily for the past 15 years or so is almost certainly the poor discipline in the classrooms, where students mess about and adults have little recourse other than to beg and plead with them to behave.
So yes, I worry about slippery slopes and I wonder where this is headed.