But if you modify the binary, you'll need a jailbroken phone to decrypt it first. If an unencrypted binary is leaked online, you would still need to jailbreak your phone to run it, or you'd need to pay up for the ios developer program, and re-sign the app with your own certificate and make sure to modify all the app IDs embedded too.

Significantly raises the bar for casual cheating.

Edit: Oh, and if it uses game center, then I think you won't be able to match any opponents since you're no longer running on the official app ID.