Recoverable and repairable armors have been a feature of OpenXCom mods for a while.
In vanilla, a dead soldier means a destroyed armor. With mods in OpenXCom, you can recover the corpse and, from it, make a new armor through a manufacturing project.
A problem arises when your soldier is only stunned though. In both vanilla and OpenXCom, a stunned soldier comes back with his armor at the end of the mission. But there is also a corpse.. which, if it is set to recoverable, will give you what you need to repair the armor, even though your soldier is also already wearing that armor. So stunning soldiers duplicates armors.
As far as I know, there is nothing to set the recovery of armor from a stunned soldier to false. Not that it would be a great fix since you would then recover a broken armor (from the corpse) from a stunned soldier, even if he has only been hit by a stun bomb..
The other way of addressing this would be to prevent the corpse recovery if the soldier was just stunned. Then you get the pristine armor from your stunned soldier and no damaged armor from the corpse. But there is also nothing to do that..
Would it be possible, at the very end of missions (just before debriefing), to reanimate all stunned soldiers? It doesn't change anything to the outcome, except that it replaces stunned soldier corpses with active soldiers, thus the corpses would not be there to be recovered.