We want to exclude matching client tickets for the first n seconds and prioritize backfill tickets to keep our existing matches full. We also don't want to take away the ability for create 2 player matches. I found no solution, just close to what we want to achieve in other feature requests like https://community.playfab.com/idea/29685/add-inverse-of-some-matchmaking-rules.html or https://community.playfab.com/questions/29974/matchmaking-implement-block-list-via-exclude-tag-f.html
Those would also be awesome to implement, but I think an ultimate versatile MM Rule solution would be the ability to hook up a CloudScript (preferably Azure function), to be able to implement any MM logic we want.