You will need to download the following tools: I've posted guides before on how to use CheatEngine to acquire Asclepius vestige part F and the Ymir Frostcores this process works pretty much exactly the same.
Theoretically, it should also be possible to acquire the Venous Claw, although I don't know it's name in the game files (yet.)
Because of this, players who would normally be permanently locked off from these weapons can still acquire them using CheatEngine and Unreal Engine Unlocker. I just made the discovery that the preorder bonus weapons (Blanched Greatsword, Crimson Longsword, and Cerulean Spear) still exist in the game files, even for players that didn't preorder.