Currently the ambitions for council positions can be exploited. If your heir wants a position on your council you can give this to him for increased stats which ofcourse is not a problem, but if you immediately remove him afterwards and wait for him to get another council ambition you can place him in the council again for another stat increase. You can continue doing this forever which gives your heir way too high stats. Just after I found out about this my newly bred genius heir easily got 40 stewardship and 25+ in the other stats while doing this for just a few years. Theoretically you can get heirs with stats over 100 if you keep doing it long enough. I know I shouldn't do this because it kinda ruins the game for me, but my perfectionist/micromanage side doesn't want to let an opportunity to make a better ruler slip.
Its mostly my own fault for not being able to stop myself from exploiting , but the exploit could easily be removed from the game by making the ambition available only once or alternatively by removing the stat boost from the reward.