In general, I was thinking about the idea of hiring mercenaries after the group stage. And I came to the conclusion that it's not fully developed yet. Hiring should be paid for in some tangible way. Even if it's in a game format. For example, it could be -5 points earned in the group stage (meaning the team could drop to 2nd place, and sometimes even 3rd - which means hiring is not available for them) - and in this case, there should be a special deadline for hiring - some kind of transitional week. Or the team should have an impeccable reputation - fulfill all the deadlines set by the tournament judge. There could also be some restrictions on the player who is hired.
In this game, nothing like that was specified, so the idea seems underdeveloped overall.