Allowing the Door Launcher to support any halfdoor as it's ammunition.

Halfdoors would need some extra values for their damage (maybe other stuff like drag too, maybe if it should burn in fire/lava) and a default value.
Door Launcher should render the correct door on the model, probably the hardest part.

Wouldn't be opposed to making the shulker upgrade enabled by default and making it only fire doors stored inside it, as long as there's some new upgrade to replace the shulker upgrade (even if it's just adding more storage slots).

Might be in a theoretical addon mod.