By United States Constitution, the governance of citizen votes SHALL fall to state governments. This is one of those "State Powers" as delineated per the 10th and final Right of the Bill Of Rights. This is a nation of PEOPLE, that shall not be governed by monarch, by tyrant, nor by military strongman. NO Federal military branch of service shall hold power of elections over the PEOPLE.
What if inclement weather, family emergency, etc etc etc FORCES people to be outside of their voting areas?? Sure if those things happen unexpectedly ON Election Day, then those people already forfeit their chance to vote unless they voted early. But for them as well as for "ex-pats", they are STILL United States Citizens, and you're taking a very grand position of over-riding what the Constitution calls a basic fundamental right of US Citizens. Not usre how you earned that position.
No one has to "sit and watch" anything. In 1776, we were a nation of some 4 million people. At the start of the Civil War, we were a nation of some 40 million.
Today, we're fast approaching a nation of some 400 million citizens, and hand-tabulating votes - even using digital computers because, after all, each and every vote entered into those are done by human hand - are going to be an inherit act of power as long as the United States Constitution still stands.
Me thinks like Donald Trump, you may want to spend some time sitting down and reading that document, once you finally get the opportunity.....