On the subject of item placement on the Anvil:
You could maybe make it so that the ingots/items you place onto the anvil snap to a position like the different weapon parts snap to each other. I'm not very savvy with the unreal engine (I've never used it before), but maybe you could create a snap-point node so that when certain items come near it, they snap to the pre-defined position/orientation and it shouldn't effect the items created from the ingots because you could leave them off of the list of items that auto-snap to the anvil.
But make it so that they can be taken off of the anvil in case you need to make something else.
EX, You're in the process of making a greatsword and a customer comes in and requests a one handed sword or a dagger and now you have to take 1 or 2 of the ingots off of the anvil to make the requested items.
Don't really know how you would do that though. I've never used the unreal engine. I've only ever used Blender, and I'm not too good with that.
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On the subject of item deconstruction:
You could make an entirely new station for weapon deconstruction similar to the crafting bench.
To solve the bug where you deconstruct an item and then use it to make a new item and it doesn't allow you to use it or sell it. you could make it so that when you deconstruct the item it deletes the items and gives you entirely new ones altogether.
This way it doesn't conflict with the item ID's and bug the newly crafted items made with the deconstructed parts and let you make other items with the "deconstructed" parts.
Just a thought.