I know I'm a newbie and my opinion probably won't be heard... But I think if the athlete shows dedication and the parent is willing to pay, then they deserve to be on a team. Strict regulations of "you must have this or that tumbling to qualify for level ..." seem kind of unrealistic. Skills can be earned throughout the season, and if an athlete struggles with tumbling, they might turn out to be an awesome base/backspot.
And regarding new athletes... my gyms junior 1 had 15 kids completely new to cheer, learned their level 1 skills throughout the summer, and ended up being one of the most successful teams in the gym.