With the 15 skins per plane limit some skins may only be "wanted" for a specific scenario rather then being a "main" skin.
As Dux said scenarios could easily use close to 15 skins per plane per side.
BoB may not be a good example because how many hurri 1 or spit 1 or 109e4 skins can you have that aren’t BoB? I would imagine the majority of the 15 skins for each of these planes would be "BoB".
However, take a Big Week or Ruhr type event.
P47s, P51s, 109g6s, 190a8s and 190a5s.
In the main we would want wider range of skins representing various time frames and theaters. Take the A8, we could easily fill up 15 skins from the west, east and Nord fronts....
These types of planes have many options for skinners. So much so that there may not be room under the 15 plane limit to create the variety of squadron specific skins for an event.
So does the 15 plane limit of skins include skins created specifically for the SEA?