...is it fair to reward only with stamina bonnus?
This gets at something else entirely than what I was suggesting. You seem to be disagreeing with the way players get training bonuses in just one skill based on their training focus as it works now. I think that is fine, and don't want to change it. Also, I'm not suggesting that players should get all kinds of bonuses in multiple skills if they fulfill more than one of the conditions I laid out in my first post, just the one for their training focus.
My point is that it seems silly, for example, for a GK to get the full GK training bonus if they don't ever have to make a save or get involved in the match. My suggestion wasn't that a player shouldn't get
any training bonus if they don't actually do whatever it is they're training to do, but that it should be less than if the player actually does (or is instructed to do) something relevant to it. I'm talking about a small effect here, too, something like PR x 0.01 when CA<LA, PR x 0.005 when CA=LA, and nothing once CA>LA.
Also, I don't think this would
...push managers to lose matches just to make sure their players improve something they cannot do....
Now while this might happen in friendly matches where the outcome doesn't matter, I don't see a savvy manager sacrificing league points for a few hundredths of a skill point for their players. Managers consistently sub in young players specifically for skill bonuses even in league matches without the possibility of the bonus I'm suggesting. For example, say you play a lineup of creative players for most of the match (and set tactics to more creative expression), and then sub in a young player at 60' who is not too creative but is training for creativity. Or you play a young GK because you are confident of a win no matter who is in goal. That happens all the time, and is precisely the point of using advance instructions to stipulate the substitution only happens if you are winning (if you care about winning, that is).
In an attempt to further clarify, the effect of my suggestion for a player with a PR 4 (and CA<LA)in a league match would be something like:0.32 bonus for playing >30 min and a 0.04 bonus/penalty for fulfilling/not fulfilling the condition
for their training focus in my first post = 0.28 or 0.36 training bonus
For a player with PR3 whose CA=LA, the bonus would drop to:0.03 for playing and 0.015 bonus/penalty for fulfilling/not fulfilling the condition for their training focus in my first post = 0.015 or 0.045 training bonus.
Basically, IMO a player should get a little more if they apply their training and a little less if they don't. That's it.