This is more of a personal dream of mine to see in any game of this kind for decades.

Backstory: In Engineering, the more you learn, the more you forget. For example, if you want to ask some basic dynamics problem, you'd have a better chance of getting an answer from an apprentice, because a Professor might have a hard time remembering those topics.

Just like that, the skills of the players are not permanent in real life. For example, Michael Jordon and Koby Bryant were still training shooting starting from 4 AM every morning, till their last professional matches. The same applies to football players like Messi and Ronaldo. Ronaldo once mentioned that his free-kick abilities deteriorated because he missed a couple of free-kick practices.

MY SUGGESTION: To set up a Bonus training plan for all players.
1. This will be in addition to the current training. They will be separate and won't affect each other in any way.
2. Users will choose an attribute to gain a bonus.
3. Every turn, all attribute bonuses will decrease by 0.1, to a minimum of -4.
4. At every turn, the player will increase his attribute bonus +1 from the selected attribute to a maximum of +5.
5. Those bonuses will be private and won't be seen by others, just like in the training section.
6. Bonuses will reset at the end of every season and after the transfers.

EXAMPLES: Let's say Player A has 60 on all his attributes.

Example 1: Trains shooting and Heading 5 turns each. 10 turns total.
After 10 turns, his Shooting and Heading will be(+5-5*0,1) 64.5 while every other skill will now be 59.

:20 Turn plans::
* Train all field Attributes for 2 days each. (all except Reflex and Handling)
Result: Field attributes will stay at 60.2. Only 0.2 gain.

* (Bonus training days in parenthesis.)
Han 58 ( 0 )
Ref 58 ( 0 )
Tac 58 ( 0 )
Head 60.2 ( 2 )
Mar 58 ( 0 )
Pass 58 ( 0 )
Dri 60.2 ( 2 )
Sht 64.6 ( 6 )
Spd 60.2 ( 2 )
Sta 60.2 ( 2 )
Pos 64.6 ( 6 )
Set 58 ( 0 )
This plan maximizes shooting and Positioning while preserving Stamina, Speed, Dribbling, and heading.

Han 58 ( 0 )
Ref 58 ( 0 )
Tac 58 ( 0 )
Head 58 ( 0 )
Mar 58 ( 0 )
Pass 58 ( 0 )
Dri 64.6 ( 6 )
Sht 65 ( 7 )
Spd 65 ( 7 )
Sta 58 ( 0 )
Pos 58 ( 0 )
Set 58 ( 0 )
This plan only cares about Shooting, Speed, and Dribling. Shooting and Speed both had a 5.7 bonus but were reduced to +5.

This system is just a fantasy of mine. It would add a level of complexity and tactical option to the game. Improving certain Attributes at the cost of others.

You could even add this system to the pre-season time, just like teams do in real life. It might increase activity and users would have more reason to check the game.

Also, you could add an option for Plus members to set their preferences and change this bonus training every turn. For example, they can set, "train Tackling, Speed, Heading in turns, trying to keep Tackling at max bonus" and the system would handle these for them. You can even call it F4 Assistant, exclusive to Plus members.

I like this idea. But instead of regular skills, I would like some new set of skills for both individual and team as a whole to be trained in this way.

For example, you could train specifically on penalties, one on ones, long shots etc for individuals, possession triangles, boxed defense, position interchange etc for teams.

That would be awesome. Teams could get bonuses for their preferred tactic, like Defense, normal, or Mixed, Long ball.

I feel like this is a long-term change, with other tactical aspects need inclusion beforehand...like more positions in game.