Just let Joe or Suzy Parent step in and make calls from behind the plate for a game or 2. Like back in the day.I saw an article about how one large tournament was thinking. Let me track it down... It was a decent attempt though probably still not workable.
Most people are overlooking one big issue.
I love my fellow umpires, but many of them fall into the 'vulnerable' group just based on their age (whether they want to admit it or not). Even if you let them call balls and strikes from behind the pitcher (which has been proposed and btw is a TERRIBLE idea) I don't see how we could locally assign enough umpires to run a tournament even if we went to one per game.
In my umpire room I would have to say at least half.
Problem solved. You're welcome.