If you're hosting a tournament like this you should have enough knowledge of the player base to know who's a rookie and who isn't and thus accept/ reject players on a case by case basis.
I would suggest a carpet ban on anyone who has ever been invited to Python's Invitationals as well as any player who's won a podium position within an international tournament regardless if they're bench or starting. If you're good enough to get yourself into a top team that manages to place in the top three you really aren't a rookie regardless. Any questionable players there on after can be assessed by the hosts on a case by case basis. The hosts get the final say at the end of the day
My biggest regret in hosting the last rookie tournament was the mentors being able to play on the ground. If you're the captain and mentor of the team and you're dedicated to your team you can just sit spec and manage the team there onwards. My rule that I implemented pushed teams like NPP, Akatsuki and Nr13 into the clear favourites by miles, it just wasn't as fair to the rest of the teams participating. Just my advice^ - good luck with the tournament