I posted this in the Match Play thread but was recommended to also post it here.
I finally had someone leave mid-tourney in a Max Match Play tournament and had a chance to put my workaround to the test.
Basically, if a player leaves I add a new Dummy Player and Dummy Arena, then I take the current match the absent player is on, replace their opponent with the Dummy Player and change their arena to the Dummy Arena and just leave them there while the tournament goes on. This way, the player’s completed games are not disregarded so their previous opponents are not affected other than dragging down their Strength-of-Opponent tiebreaker value.
As an added bonus, after missing a few rounds, he showed back up and I was easily able to add him back in by completing his match with the dummy player, and then deleting the dummy player and removing the dummy arena from the tournament.
Im sure there are plenty of ways for this approach to mess up in some way but, in this instance, it worked out well.