If I understand correctly, you don't actually use BAT, it gets consumed as you browse. You would just top it up like a pay as you go phone if you want an ad-free browsing experience, or you can generate BAT by enabling ads at a configurable level if you don't mind them.
> Eg, I pay $5/m or $15/m, whatever, and that gets split up by the number of pages I view and content I consume.
That's 100% possible to do with Brave's system.