But players growth rate decreases when he becomes scout.
Take screenshot of your training when player has 5* and when he has 6*
Skill progress per lost condition rate changes.
Yes, but the only way to avoid this is to give the sp to special ability or a second role - not saving the sp.
Also, the red star isn't like a switch that makes the gaining to drop abruptly, but gradually like this line chart.

pre 6-stars, where to spend Skillpoints?-gaining-chart.jpg

Consider this like a 6* player, but Q0 or Q1 in comparison with a 5* player but Q9. The quality is near.
Sometimes the 6* (but Q0 - Q1) player can hit a bigger number than some of the numbers he had when he was 5*.

ps : great posts and advices . Pal, you should right them down and try them