What you seem to be saying with your RL analogy is that any team in division III or lower should sell NT caliber players to teams in higher divisions. Right?
Please don't infer this as meaning that I believe the best players should be given to the top teams
It's up to the manager to hold onto a player or not, even if they choose to hold onto a very expensive player to the detriment of their own club. A manager's goal should be to win and promote, not have the best player(s) in the world. or that top teams should be entrenched at the top. Movement between divisions shouldn't be reliant on having one amazingly skilled player over having a depth of good players.
I think I did, and I apologise
Also, a very good player could come out of a regular mutli player system and now even more so since they'll be doubling young player training.
Most of my concerns with making it worthwhile to win and promote are due to experiences in hattrick. Long term, it seems better to sit it out in lower divisions than to aim for DIII and above.