You might be able to use your router as a workaround. Some routers have parental controls on them that will allow these types of restrictions.
For example my Fritz box still sees the device on the network, even though it is wirelessly connected to the Koala Safe (network, which is connected to the Fritz box, which has the Internet connection)
So I can apply a filtering profile at the router still, that includes setting a maximum amount of time someone can use the internet connection on that device for each day.
Most parental controls on routers don’t seem to be very granular. For example in our case after the limit is reached it means no more internet access until the next day. So we use it as a way of getting our daughter to do her homework first, and have the discussion about work before play.
Hope that is a help