This mod makes all mannequins bald, so that they only display chosen hair or hat if chosen in CAS.
The mannequins are generated above the ITF object galleryShopClothingPedestal, which can be customised with "testingcheats on" and cntrl+shift and the custom Shop for Clothing Display Pedestal Mod "ani_ITFClothingPedestal" by ani_ with more interactions found here:
https://modthesims.info/d/525365/sh...destal-mod.html
The Clothing Pedestal and the mannequins are available with the "Into the Future" expansion, which is a required.
The bald hairs are "Seasons" alien hairs and I don't think Seasons is really required, because if hair is invisible would also make all the mannequins go bald.

Although I don''t really play with the clothing pedestal, it was annoying me that hairs could be selected but mannequin also keeps the default hair once exiting CAS.

Side Effects / Note:
1. If any hair is selected from customising within CAS, any sim buying the outfit would receive the new hairstyle on display, and if hairs are locked, to all outfits.
2. If no hair is selected or if as is, the mannequins will always be bald by default, and bought clothing won't affect hair.
3. The original hairs will appear in CAS as always but will have a custom category logo because of renumbering.
4. The duplicated bald hair overrides are categorised as "hidden in CAS" could show up with unlock clothing or with "Twallan's" nraas mod set to show hidden clothing.
5. Game sims wearing the same hairs will go bald plus depending on which pre-made or saved sims are affected might need their hair redone in CAS, unless you think it's funny.

Future improvements and ideas from other modders
The best way would have been to find the SIMO "outfit" files for each mannequin age & gender and remove the hairs, but:
If the default hair does not go away after changing the hair in CAS, means it is referenced somewhere, (can't find anything) in one of the VPXY, XML, OBJD or OBJK resources
I tried cloning the MannequinSim.package and it does not reference any age, gender, mesh or show any other searchable resources asif each mannequin is a hard coded premade sim?

Additional Credits: S3OC for cloning hair packages and renumbering them, before and after exporting contents to a new package with S3PE for editing the package contents.