I think there are some very good quality of life changes there. Sounds like rather than having two people with head coach powers, we can have a different set of powers for the assistant. Scrimmage finding is definitely a good idea. Scouting will definitely be a help, but the question is how - maybe assistant coaches have a special feature where they can scout without calling players up to the roster? This ability would not be available to NT coaches, they're powers will still be unchanged. This kinda makes the role of assistant coach a bit more special. Plus, since we are going to have an official NT scouter... Special access to that for the assistants?
I don't know how the "proposing lineup" thing would work from a programming point of view, but maybe we can "lock" the lineups once the NT coach sets it, like what slamdunk9 mentioned? This means assistant coach can set as many lineups as they want, but once the NT coach sets it, the assistant won't be able to overwrite it. It should ensure that we won't have to worry about NT coaches forgetting to set lineups (unless both of them forgets), and that we don't have to live on "trust" that the assistant coach won't undercut the NT coach and set a last minute lineup.
I think this would be workable. Tho how we select them *might* require more thought.