No one is stopping you from offering your ideas to E* or D*. In fact, good luck! But it won't wash. The gov't, believe it or not, is actually helping you by requiring the exemption for receiving the DNS network feeds...if your local affiliates approve the request. But that is limited to the East/West Coast "mothership" feeds from the network sources themselves. Those networks are on CONUS beams and reach everyone who is allowed to get them. But the non-NYC/LA feeds are all spot beamed so no dice on getting anything else.
While you may claim to not be watching the local channel(s), you are still a member of your DMA as counted by the local affiliate. Those numbers are used for their ad sales. They don't claim that xx% watch every ad...they simply tell the prospective vendors/advertisers that "there are XX people living in the market and you have the opportunity to reach them if you buy ad space on our channel".
And I think TexasBrit answered the main questions quite well. If we were to do as you suggest, we lose the local markets by attrition, then the networks lose their kickback on ads and we lose better programming. D* loses money because the networks would try to bargain up the price per sub to cover the loses down the stream, and more people would say no thank you and find another provider. So you have now single handlely killed broadcast television.

Congratulations!!
It's not THAT bad...I exaggerate for emphasis. But the way we have it works. Can it be improved? Sure. Allow us to select a neighboring significantly viewed network, but that is for overlapping DMA's....not hundreds of miles away. And there may be other simple ideas out there. But what you are suggesting WILL NOT HAPPEN