This would turn the Internet into a hell scape if only because corporations could throw huge amounts of money around.
There would be incentive for the Pizza Huts and the Walmarts of the world to just assume control of the websites for any local competitors.
Yes, it’s possible
You need a SIP trunk to connect to and a PBX server. I would also recommend a proxy server to obfuscate your SIP server as it will be constantly attacked.
It doesn’t technically need its own network, but having it on its own VLAN is recommended as you will want to have some QoS policies for the UDP voice traffic otherwise your call audio will be choppy