PCEAr has been updated to 1.4.1. It's a little update that supports 4 new unique armors: General Tullius' Armor, Ebony Mail, and Party outfits (body and boots)
As a reminder, if you missed update 1.4.0 (or just plain a new user), Nightingale and Guildmaster armors are not redirected the "conventional" way. They will still use the original ARMO, only they'll have new ARMA for you to fiddle with. This is to allow them to be recognized by the quests they're needed in.
What does this mean? This means, they'll conflict with any other mod that modifies those armors. Off the top of my head, USKP already conflicts with Guildmaster armor.
Since USKP always loads after PCEAr's master, you'll need to create a plugin that intentionally causes Identical To Master record to preserve them.
This may not be the most ideal situation, but at the end of the day, it works with my configuration, and that's what modding is about for me.