Nice job. I can't seem to get good-looking skins for your factory ship, so I'll try skinning this thing. Most important of all, the NPTR funnel = funnel logos for civvy skins!
Is the ship armed later in the war?
RE: nationalities - If you want to use the ship as a stand-in for generic vessels I highly recommend adding it to the Swedish & Canadian rosters. IIRC Canada at one time owned the "C.O. Stillman" - possibly the largest WWII era purpose-built tanker at over 13000 GRT. Canada also owned the Imperial Oil ships, which were up to 11000 GRT - unfortunately several were lost in "Drumroll" circa 1942. Sweden had several large tankers, but I don't know of the class names. Same w/Mexico and Argentina.