DISCLAIMER: The armour we saw was a bug and might be scrapped idea rather than future content. If that's the case, this whole thread is pointless.

Since germans might get body armour, why not add something similiar to commonwealth as well?
The only problem with that is that british didn't used armour in the field, instead they issued armour to tank crews to protect themselves from shrapnel. I guess this could be played off as if the tank crew have left the tanks to fight outside, seeing how many empty tanks there is in maps similiary to "The Black Panthers" unit in vanilla DOI.
The armour was usually made off a lether / cloth west that had metal plates clinged together on the vest with chain mail. There's also some variants with it being made fully from chainmail, but it's quite rare. Pictures for refrence:
https://flashbak.com/wp-content/uploads/2015/03/3068488.jpg
https://www.iwm.org.uk/collections/item/object/30015940
The general idea of the armour is cloth / linen thick vest with metal plats that are held together by chainmail. There's also a helmet with a face mask / chain, but that was used more by the french and austrians, besides it wouldn't have any effect on the game, thus it's not worth even modeling it.
Gameplay wise, the armour should only have 3 purposes:
1. Protect the user from long range fire.
2. Slightly protect the user from explosive.
3. Protect the user from ranged sidearm fire.
The armour should be also restricted to late and mid war maps.