@angelD: a lot of that stuff is available with Change Sim (option at the mirror/dresser/closet) without any cheats, but yeah it's limited to household members. There's nothing against changing the outfits of NPCs if you can get them near a closet and that's a good 90% of what makes NPCs offensive anyways.
While we put a limit on when and how often you can change the gender status of a sim, there's a lot more open in Change Sim and we've never found a reason to ban it. Without any cheats enabled, you can still change the name, facial features, skintone, and body shape of a sim except for their weight and fitness. It doesn't affect age or the actual challenge.