i am not opposed to this idea but having a "physical" bag does give the sliding player something to hook on to and also the fielder to "find" with his feet when it's a force play.
hows this for technology -
My 14u team has been playing in a winter league that is strictly in a batting cage. you choose 5 players for each game.
a pitching machine is set and hitter contact is analyzed by a computer tracking system and simulated results are projected onto a display. no running, no fielding. just hit the baseball and the computer tells you what you did (hit, out, gidp, sac fly, etc).
¯\_(ツ)_/¯