Their near/intermediate future is tied to their current QB. I see nothing wrong with giving him a coach he’s comfortable working with and either sink or swim. If it doesn’t work, it will probably be time to move on from Allen and the HC (and GM) all at the same time in 3-4 years. You can trade him in his final year(s) of contract and start from scratch.
needle moving head coach moves are for teams in desperate need of change. Buffalo just needs improvement, not an overhaul.