I think that being able to violate a contract (at some cost, perhaps reputational) when the motivation is sufficiently high gives some spice to the dynamics of negotiation.
Technically, if you let players make arbitrary contracts, then they can add that themselves, by making contracts along the lines of “I will either freeze that lake within the next 5 turns OR pay you 10 gold”.
It might be helpful to think of the game as defining the maximum penalty for breaching a contract, rather than “the” penalty. If the game says that breaching a contract is death, you can say “I’ll either do X or skip a turn” to create a lesser penalty. But if the game says that breaching a contract only makes you lose a turn, then you can’t write a contract that will kill a player if they renege, because they’ll always have the option of losing a turn instead.
Technically, if you let players make arbitrary contracts, then they can add that themselves, by making contracts along the lines of “I will either freeze that lake within the next 5 turns OR pay you 10 gold”.
It might be helpful to think of the game as defining the maximum penalty for breaching a contract, rather than “the” penalty. If the game says that breaching a contract is death, you can say “I’ll either do X or skip a turn” to create a lesser penalty. But if the game says that breaching a contract only makes you lose a turn, then you can’t write a contract that will kill a player if they renege, because they’ll always have the option of losing a turn instead.