I have a family member who uses TONS of data, much more than anyone else in the house. Sometimes it affects my ability to stream or game the way I should be able to with a 1000/1000 connection. What I want to do is limit his bandwidth on his devices (phone, iPad, laptop, and smart TV) so that he can't eat up bandwidth that I want to be available for other things.  My new A20 does give me some per-device QoS, but it's not really adequate and I want more granular control like I find in the emulator for the C20 router.  

Is there any way to do this with the A20, or would it be possible to just plug a C20 into the A20 and set up a separate network just for him that has bandwidth control enabled for his devices? Is there a better option for this?