I believe the contract with Leon is rather fair in my own opinion. It merely enforces cooperation and no backstabbing. Leon even was smart enough to think of multiple outs to it should the party in question need to nullify it. It also needs to be signed willingly. He's up front about it, he's protecting both parties from the masters in question, and it allows both, if they agree to sign it, the clean mind to not worry about any death threats on their heads from their new ally.