I've had a few frustrations where a player wants a new contract, but their agent locks in a request such as 'Will play in Position A with Role B' that proves a blocker on the whole contract because it's not where he's been playing, or indeed a role in our system. So I really need to be able to tell him, and his team-mates if they get unhappy, "I'm not changing our entire system for one player". If he digs his heels in at that point, fine. But as it stands it feels like there's one little thing that, in real life, I'd explain to him "Your agent is blocking your new contract".
In general, if there is one sticking point that an agent has locked in, I'd like the game to have the capacity for me to tell the player what the sticking point is. I had another example where the agent was trying to reduce the minimum release fee by a relatively small amount but had capped it so I couldn't even take it to the existing level.