If we buy 4 star young FTs, it only cost 30 plus greens to train a 50 SA with world class regimes. We should also try to use those drills which the player has low skills. I think it isn't costly if keeping player for a 5-6 seasons. I can't tell it is effective but I have been playing without SA and support and do ok. I read there is an effect but is minimal. But alot of things have minimal effect but might be substantial when combined.

SA, bonuses, attendance, support, morale, condition have all been said to have only a little effect but when you have it all. It might just be what helps you beat a troll result for example.