If I complete a mission that unlocks and gives access to new equipment such as the scorpion hedgehog, do all of my characters have the scorpion hedgehog as a craftable item or do i have to complete the same mission with each of my characters?

those unlocks have to be done per character I believe.

Originally posted by Schalimah:

those unlocks have to be done per character I believe.

Seems so.
At least my open world char can't craft scorpion defences. The carapace mission is done with another char, checkmark ok and had to craft them in mission to complete it.