I don't know about "reasonable" or "unreasonable". I do know that there's no way I'd allow this in my network. My DHCP servers point to my own DNS server for a good reason, and I am completely invested in ensuring that nobody bypasses it to the best of my ability.
I cant wait until 8.8.8.8 becomes the "address" of the local DNS server as more and more people start to hijack it. We had to hijack it at my old work because some random vendor's devices were hardcoded and we needed them to see our internal names.
I'm actually surprised that more networks don't route the addresses of all the public DNS servers to their resolver.
Then your network is a private walled garden and not "the internet", and I don't know why you expect consumer devices designed to be able to get to the open internet to work unmodified.
I mean, I'm sure your decisions are made with the best intent, but how is what you're doing any different technically than the DNS hijacking the Comcast et. al. have been caught doing?
This is true of all LANs.
> how is what you're doing any different technically than the DNS hijacking the Comcast et. al. have been caught doing?
It's not technically any different. However, there's a very huge non-technical difference: it's my network, and I have every right to configure it however I wish. When others engage in hijacking, they are interfering with traffic they have no right to be interfering with.
Because he's doing it on his network with his devices that he paid for.
He's not meddling with the traffic of paying customers.