I'm sure Russell would prefer to keep Bevell. But he's still a young guy who hasn't experienced anything better in the NFL.
He needs an OC who can challenge him to be great, not a buddy. Adding any new play caller will be like doubling his knowledge. He won't like it, but it's what the team needs.
This is why I want Pete Carmichael for OC/Assistant Head Coach. He's worked with Brees for years, has a great sense of offensive flow, and always remains committed to the run. In that case, maybe they should re-sign Jimmy Graham; Carmichael actually knows how to use him after so many wasted years! Perhaps Myles Gaskin could play the Alvin Kamara "gadget" role.