Quote: "You don't have to do any coding, just use scripts that are already provided or any on the many given away on these forums or as a last resort you could always buy scripts from the store."
This is true, there are a lot of options out there that doesn't require you to actually script the game yourself if you want features that are not in the default scripts.
Quote: "if you save to a file you will dramatically increase the complexity of testing your game"
This I see and agree with^
Quote: "and also open up the possibility of users 'cheating' by editing the file themselves, for example if you stored ammo count in a file to load in a later level someone could simply edit that file prior to the level load and give themselves extra ammo."
This you can do with standard save files anyways, and seeing as these files would be updated right before a level switch and only pulled right after, it would be way easier to just use the savefiles for this purpose.
Anyways, cheating in a single-player game is pretty much piss easy in any game, because you are only ruining your own experience.