[Official] Player Attribute Cap

[Toxcatl]

Be exploited to do what ? Seriously !

There is no exploit by increasing another skill relative to the drill you run if one of it skill is already at the max .

Assuming your idea is implemented.
If you have Fitness and Speed 340%, then Dribbling can be trained with Sprint three times faster than usual. After that Passing can be trained in the same way (Slalom Dribble), very-very quickly. You got the point.
340% is not that much, some of my 18 y/o already have Fitness and Speed 250%, and I didn't train them with Long Run (the fastest way to increase these skills).
No, I think this is a bad idea.