The new cosmetics are terrible if you can't mix and match head gear with outfits. What's the big idea only giving us one item per skin this time? Why would I want them now?

Warhammer: Vermintide 2 Gameplay Feedback
8

It is indeed confirmed
Source: The Mythic Masquerade helmets and body skins are not separately equipable - #3 by FatsharkLev