It won't work. Forcing player to extend his contract or leave from the club will not work. It's all depend on mbappe itself. I meant once you were forcing a player and you must also aware that if personal agreement actually required for a player to leave from the club. If mbappe will not be even agree to the personal agreement with new club and what you can do just terminate his contract to leave from the club as free agent. That means you will be got nothing from him at the end of his contract.
This makes PSG dilemma to determine which the best decision for him. To keep or sell him until his contract will be running out. Mbappe is wanna leaving from there with free agent caused by he will able to pick which team that will become his next team.
That's why PSG feels difficult to determine the best decision for mbappe. Mbappe forces himself to stay until his contract will be running out.