I really don't like this argument.
Regardless of what is generally regarded as actually being the reason, student athletes are given scholarships on the basis of being a student first. Transferring holds up their athletic eligibility but not their academics
For coaches that is their job. They can move around just like any of us are free to move around in our jobs.
If you want to get rid of the sitting out a year then take athletics out of college and just make it a independent minor league system. This gets rid of the facade that most of these high level kids are there to get an education
I'm not sure I follow your points.
They are by definition, not given a scholarship on the basis of being a student first. It's an athletic scholarship, not an academic scholarship.
A minor league system isn't a practical solution for anyone. There wouldn't be any interest and for the vast majority of the kids that want to earn degrees, there's no reason to forego college to play in it.
If a coach leaves or there are extenuating circumstances, then kids should be able to leave and play. But having kids actively recruited on their own campus to leave for a different school? Sounds like a massive can of worms.