I can definitely see what you're saying. I wholeheartedly disagree with you based on one point. It absolutely does **** having teams resign all their coaches, blocking them from possibly being signed... even if it's a promotion from a Position Coach to a Head Coaching position. Why I have to disagree with you is because Head Coaches going into each offseason should be your number 1 priority in the coaches signing. If you want a coach, simply pay them more money than other teams are willing to bid. Houston had a coach, OC Gilbert Boggs who definitely wasn't at the end of his contract, in which they tried to resign for a total of 112M/6Y. Cleveland swooped in and was able to nab him to be their new Head Coach at the price tag of 180M/6Y. Basically with the example and the sole reason why I'm against your point is that if you want a Head Coach (Who should be your priority anyways when signing coaches) then you have to go after him. Not with a low ball deal, but with a massive contract. I noticed you offered coach Dan Compton a 28M/3Y deal. He's a great coach and I would've been shocked if you were able to nab him. Atlanta rightfully offered him 109M/6Y.
My mindset when looking for a Head Coach is to give him a huge deal... low enough that I'm still able to sign my coordinators to a deal that other teams would have a tough time matching, but high enough that I'm sure to get them. If there's any money left, that's when I throw the rest of my budget on maybe 1 position coach that really should be a coordinator, or spread it out for a couple of decent position coaches.
In the end, coaches matter for 2 things: Player development and a Head Coaches' playbook. I've yet to notice a huge difference in player development between different teams/coaching staffs. While they do play a role, it's not to a big enough degree that I feel like a rule restricting owners from offering coaches, with multiple years on their contracts left, an extension.