Or maybe it's a setting on each category as to whether to show it if there's no permission. It's default setting would be calculated statistically just how allow-ratings is.
What I said to a customer, which is an extension of this for Download Categories (let's you fully browse the category, just not download):
You'd be able to browse through the Download Category before purchasing full access, but any attempt to download a Download would take you to a purchase screen). There'd also be a message over the top explaining this, with a link. This will allow a customer to see exactly what they'd be purchasing. Time: 2 hours.
This is now implemented for 10.1 for downloads as a global option, and actually I don't think it makes sense to do it for any other content types. Downloads are the only one where the main goods are separated from browsing.
You'd be able to browse through the Download Category before purchasing full access, but any attempt to download a Download would take you to a purchase screen). There'd also be a message over the top explaining this, with a link. This will allow a customer to see exactly what they'd be purchasing. Time: 2 hours.