You need to consult a Lawyer before you go live.
The thinking you are using did not work for Napster, Napster argued that they were not in control of how the users shared the content, they were just a vehicle to share it on. They lost in court, so that might be one precedent someone uses to sue you.
I am not a lawyer, and I do not play one on TV, so please contact a lawyer, spend the little money it will cost you to have a two-hour conversation, and make sure you are covered.
This creates the potential for significant liability for you -- including personal liability under federal copyright law. Definitely should think twice before proceeding, unless you plan to operate entirely outside the US.