I have the Mark III. Can you explain why you would want to change the loaded chamber indicator and magazine disconnect? I'm not sure I understand the advantage of modifying the pistol.
The LCI can contribute to malfunctions (failures to extract, IIRC) because of the way it rubs against the cartridge casing. But, in fairness, it's unlikely to be an issue unless the pistol is already very dirty.
The mag disconnect prevent magazines from dropping free on their own because of how the disconnector "switch" (for lack of a better term) drags against the magazine.
I don't have any specific objections to either one (in a target pistol, at least), in fact they're probably a very good thing to have if you're using the gun to train new shooters. I tool them both out of my MkIII simply because they don't offer any benefit to me.