You don't need to necessarily formalize game theory to consider things like: hey, we just gave the president the authority to pardon. Couldn't they abuse that? What if they pardon someone who was doing something illegal that they ordered? What if they commit a crime and pardon themselves?

I mean, that's the most obvious one that you don't really need formal game theory to know could be a problem. Then there are all the other problems. Checks and balances are good, but when a powerful faction uses its power to put loyalists into the thing that's supposed to balance them, the system seems to unravel.