There has to be at least 7 to start the game.
If enough players are sent off (shown the red card) to get below 7. Seven players the game is terminated.
Coaches are given cautions at any point in a game. A referee may verbally warn a coach for unresponsible behavior, might even send a coach from the game. In this scenario, if the coach is not verbally abusing the referee, the referee cannot discipline the coach.
The question is a coach dumb enough to have five players ejected from the contest? Verbal abuse usually has a stiff penalty (3 or more game penalty)
Food for thought, depending on the competition, the penalty might carry over to the competition's next stage or following year?
Now the league could take additional action with the coaches from an administration.
Bottom line, this is not worth the risk.