There is some precedent. The Tomlin thing is a good example. Completely different era ... completely different circumstances ... but John Madden was 32 or 33 when he was elevated to Raiders' head coach by Al Davis.
It may also fail.
From where I sit ... I would much rather this franchise make the grand gambles - INCLUDING shipping all those draft picks to Tennessee to draft Goff, up through bringing in this young kid as head coach - than attempt to play it safe and get by.
Besides ... if ... if McVay would be fortunate enough to be able to bring in Wade Phillips ... that would be a win/win in ways we, as fans, might never understand. It's too easy to categorize Phillips as a 3/4 DC. As has been noted, his forte is in adapting his philosophy to fit his personnel. He is an extraordinarily underrated coordinator. And ... perhaps more importantly ... he's a good ... man. He treats people well. He gets the most out of people by playing to their physical and emotional strengths.