Agreed. A great bunch of highlights overall. I too don't think the Fog gets an invite for 2020. I think it's important to have 3-4 new members for each team the following year, to spice things up. Sure, it could turn out worse, but it could also turn out better. But the important thing is, it won't become stale with the same line up year after year. Just keeping the staple 2-3 players like they've done in the last 3 editions is fine (TE's Fedr/Z, TW's Sock/Nick/Isner).
As for the rules in case of a w/d, they can simply have a rule that when either team pulls out a player, the alternate is automatically subbed, full stop. This way, when they submit their line-ups, they know well ahead that it's always a possibility that any of the scheduled players could be replaced by the alternate. Simple, straight-forward, and no confusion like this year's Rafa/Nick w/d.