I didn't check any code if it's catchable somewhere but I quickly wrote some code. This is indeed a nice idea.

Quick thought: provide also a "pickup" command for the furnace and/or upgrade command for the foundations because once placed, the foundation cannot be upgraded.

Maybe there's a more elegant solution but I won't be able to look into it for a while.

We will test a basic version on our server.

Item 'furnace/refinery) gets deployed when having it selected in the inventory belt and using the use-key. The middle is the spot where the player was looking at.
There's a basic check if no other items are in the way.
The item can be picked up when using the hammer and using the use-key.

I hope to find a solution for keeping track of conditions as by default, the furnace and refinery have no condition enabled.
A basic solution woud be that a player cannot pick it up unless the item (entity) has full health.

Any ideas or tips are welcome.