It's pretty easy...
Verizon Communications is already testing (prepaing to...) this method in several markets. It is exactly as you described, but forget the "Top 20" stuff. Everything will be an on-demand stream. Every show that a network has to offer would be available for you to pause, fast forward, rewind, and summon at your bidding, without the use of a DVR. Now, one could watch "live" programming, that would basically be the time that a network, like Discovery, first makes a show available. I'll get back to this column with the link to Verizon's service so you can read more about it. They are taking a balls-to-the-wall approach by bringing fiber optic right up to one's house, and delivering uber-bandwidth so that these streams will be possible.