What you are suggesting in turn is in fact the old studio system where a studio had contracts with everyone from stars down to dressmakers and technicians. For a variety of reasons, that has given way to the current model where artists and technicians are not guaranteed income beyond one film.
In the contemporary marketplace, where the only starting options for nearly all young filmmakers are unpaid internships with zero real creative opportunity, a three year contract at $30K/yr to direct, write and edit feature length films would be a no-brainer. Steven Spielberg doesn't have a contract with Universal because he's already Steven Spielberg. The guy who's going to replace him has no clout yet, and would jump at a an exclusive three picture deal, no matter how low the pay. There's a reason that Roger Corman never lost money, and it's probably related to his focus on fresh talent.