If I may give a suggestion to the OP, until a solution is found within BS.
Prefix Pset, is according to your need, switched to something like:
Req_ for Required
AsB_ for As Built (if you need to document it, otherwise I’d leave it).
Add_ for anything extra you may add, outside of established Psets by BS, Client, x.
Add Req and AsB as suffix to parameters, where they have a equivalent BS *Common one.
Req_DoorCommon - FireRatingReq
AsB_DoorCommon - FireRatingAsB
Add_DoorCommon - HasFunctionX
This is how I recommend it in Denmark, and similar syntax for requirements, is widely used in Norway.
While not perfect, it’s functional today. And naturally, many other methods could be used, nor problem. Just make sure that you document the one you pick.