Ah, sorry, your initial post sounded like it was talking about the Prefabs. Although the names ‘Prefabs’ and ‘Archetypes’ are irrelevant, they’re labels for different types of functionality.
I’m due to look into creating Pickups in a similar fashion to what you’ve got listed above, but Epic recommend the parent / child Blueprint method. So I would create a Parent generic pickup with an enum that lists all the types it could be (extra health, extra armour, extra ammo of type) as well as default value for that pickup type and an empty mesh slot for that pickup type.
Then I would create child Blueprints of each variant I need, set the enum type, the appropriate value and a mesh in the Blueprint. Then drag and drop the children into the level. Is that not possible?