Originally there were things called POP's (Points Of Presence), and you had specific numbers all round the country. Back then I was with Demon Internet, and the number I dialled had SIXTEEN lines only - it was a Sheffield number, and covered a LARGE area - including Hull. This was a problem, because Hull has a private telephone system (even today), and it allowed unlimited local calls for 5p - as the Sheffield number fell within 'local calls' some idiots in Hull left their modems permanently connected, reducing the 16 possible connections. The eventual action taken to prevent it was to ban Hull residents from those numbers. I don't know where in Sheffield I dialed into, but from Sheffield there was a 64Kb line that transferred the data from the 16 modems to Demon's servers down south.
This was how all domestic Internet connections were done.
Demon then introduced VPOP's (Virtual Points Of Presence), I believe Demon were the first to do so? - and this is what still happens today. Essentially it needs a MUCH larger infrastructure, if I remember correctly it was one of the large electrical power companies?, and they ran high speed network lines all round the UK - one method was a robot which ran along the HV pylon cables and spun a fibre-optic cable around them. This allowed them to build a country wide network very cheaply - no digging roads up or anything.
So your call now went to just one number no matter where you were, and your local exchange transferred it to the power companies network system, then from there to your ISP's servers (in my case back then, Demon).
Demon obviously had to pay for the use of the infrastructure, but no longer had to build and maintain small banks of modems around the country, and pay for poxy 64Kb lines to their servers.
I rather suspect that you haven't really looked into the logistics and costs of what you're proposing? - if it was easy (and cheap) it would have been done years ago!.