Main Pro-Sites Level the only level and premium.

I would like to allow my users to sign up to a Pro-Site without having to pay and still have premium access. I only want one level (premium).

However it seems I have to manually upgrade sites in order to give my customers all premium without them going through a payment process.

Is there a way to offer a Single Blog Type (premium).

I just want to be able to control plugins and themes - no interest in charging for blog levels.

Any help would be great.

Paul