I think if implemented there would a massive conflict of interest because those paying for Facebook premium are going to be the individuals advertisers are targeting most, especially if it's $10 per month.
It's essentially saying lets remove all the people with disposable income out of the eye of the advertisers. To me this seems like biting the hand that feeds.
~10% complete and already looking for payment seems a little preemptive to me, guess you can always refund. Other than that the overview of content looks very relevant, will be interested to see the finished product.