I think while things may complain simply pulling the power to the ISP modem/router and doing a full shutdown of any phone would replicate what they are doing. I

I think while things may complain simply pulling the power to the ISP modem/router and doing a full shutdown of any phone would replicate what they are doing. If you wanted you could have a separate AP from the router that could stay running even when the router loses internet to keep the local network running, but if we're being honest... does it really matter? Most devices might complain, but most will simply stop working silently and then reconnect when they have a chance. Some might need to be power cycled because they gave up trying to connect (I had a smart garage door that had bad connectivity and would sometimes do a version of this).