I remember seeing this tweet a few months ago
That looks like a brilliant idea; building capacity, providing the opportunity for more players to play.
The downside is that the clubs and teams with a depth of talent can fill their bench with 9 players and resupply their team with more world class players when the first 11 get tired. Smaller clubs won’t have large squads and it might mean forcing youth team and less experienced players into the frame earlier than necessary.
The clubs ultimately decided against the idea.
Pulling a lever in one place will have effects elsewhere. You need to understand some of those effects before you start to pull levers.