Ah, I see. Fair enough. I would probably add in that case, to maybe add some more attributes level up to what you made in modifications. Just so the player can still level some attributes, while training those plans you added.
Say for weak foot, also add ball control, as it would make sense that it would improve as a player practices it.
For Skill Moves, maybe dribbling, as a player would become better at that as well.
For Defensive Workhorse, besides interception, I would also suggest Defensive Positioning, as that would play hand in hand with defensive training (plus maybe balance or strength. (I would imagine player attributes are capped to a degree, so even if you go from low to high), someone who has maybe 50 strength, would probs go max to 60?
For Offensive Workhorse, personally I would go with Offensive Positioning, coupled with maybe acceleration and/or speed + short pass. As players would be training to look for gaps in space, and that seems to make the most sense and look to pass quickly.
Could I also suggest maybe a SetPiece specialist plan? For FK, Long and Short Pass, Long Shot and/or Finishing attributes? Considering the diversity of skills in attributes, even on a standard growth, the differences would still be diverse.
Also maybe if you could, you could dm me about how to modify training plans. I have some ideas, and was thinking maybe I could do a mod that works congruently with yours, for those who would like to have an option?
Sorry for the long text.