Your approach is probably the only solution right now. I generally don't think ahead but that's what it is going to take. :)
Wndblwz I just got the chance to test this in a couple of different settings, I used the "Ask to see outfit" social at a festival, picked their Party outfit and the Sim that my Sim was chatting with changed into it and stayed dressed that way. I couldn't remember if that social caused the Sim to keep wearing the outfit that my Sim asked to see or if they'd only change for a minute. So that could at least work in a social group if say you gave them all a crow outfit for example and travelled as a group then got your Sim to "Ask to see outfit" for each of their travel group. It would be tricky if not in a social group because you would have had to add the outfit for random townies and then befriend them and that would be a lot of work.
simsplayer818 I appreciate your testing this! I use the "Ask to see outfit" social but what I want is my Sim to be dressed in the festival-appropriate theme... It seems NPCs always show up dressed according to the theme. Now I'm just using your suggestion to have the festival attire in my Sim's wardrobe.
