This will be awesome, same for Netflix. Another problem to fix is limiting watching to certain times and durations. I wonder if there are third party apps that aggregate across YT and Netflix and has these features in a legal manner.
For the time limits you could take a look at Circle, which allows you reasonable control (at an individual level) of when and how long your children are using Netflix etc. And offers some control of what (by classified type) or domain whitelist/blacklist. Don’t think I can block specific urls so can’t achieve whitelist only YouTube.
I've been looking for a router with good monitoring and control for years, this looks very impressive, thanks!