Using builtInWeaponSets to add a dummy item with recoveryTransformations to change it back to the original item could probably do it.
Something like this:
units:
- type: STR_EXAMPLE_UNIT
builtInWeaponSets:
- - STR_DUMMY_ITEM
items:
- type: STR_DUMMY_ITEM
fixedWeapon: true
recover: true
recoveryTransformations:
STR_EXAMPLE_ITEM: [1]