Happy Thanksgiving... I have simply been using "Asset Editor" from my "Days Gone" modding escapades to both unpack and repack these S.T.A.L.K.E.R. 2 .pak files. It works perfectly and is ultra simple. The link to Mod Database (Trusted) is below for your convenience. Currently educating myself on extracting the .ucas files. If you have any insight or can point me in a direction that AI was unable to, I am all ears. Getting "UnrealPak Viewer" to function for me is proving to be quite challenging. Regardless, best to you! (Only my second post EVER! lol)
Unity Asset Editor v0.2 file - ModDB