I agree. I feel like Vladdy would buy in, he's lost weight before and wants to be great and carry his team. Kirk has come into seeing training just as fat each season and I'm assuming management has encouraged him to change his diet and exercise plan, so maybe a more strict process should be implemented for him.
Manoah is where this gets interesting. He's up his own ass and is already fighting the FO tooth and nail and refusing demotions. He's entitled. He's also a guy that's prideful of his own gym and his offseason plan and tweets responses at any media member bringing up his weight. I'm not sure how you'd get him to buy into anything. Maybe you just leave him to his own devices and see if he figures things out on his own for next Spring, but you sign a 5th starter type regardless because you can't rely on him.