All rotations

Team A receives serve in all six rotations. Only team B serves. Both teams move to the next rotation when team A has scored twice in a row. Once team A has received services in all six rotations, new teams are formed.

The number of players in team B depends on the number of players available. If team B consists of only two players, you could change the rules for team A to ensure that rallies aren't over almost immediately. For example, you could force team A to attack from the back row at the start of each rally.