From my understanding all Arcanist's weapons are custom as the geometries contained within the tome were likely inscribed by the Arcanist who owns the tome, even if they were all copied wholesale from another tome(s), the particular order is likely to be unique to that one tome. For other weapons I'm on the fence-as long as its not to out there(read gun-anything, buster swords, etc) then I don't have a huge issue with it. If its something as similar as saying theres a scratch from this or that then thats totally fine.
Avatar by DimmerMeerkat, go check out their commission thread! Clicky!