The variable labeling idea should work. So you want it so that if an enemy player is dead, THEN you can get the items that he has, else the items can't be picked up, right? Sorry, didn't really understand the question.
you could set the custom value of the item to the player number and when a unit acquires the item, if the Player Id does not match the custom value, drop it
I do know this - xenforo dropped the ball by not keeping the vbulletin reputation comments as a feature. The loss of the Reputation comments data when we switched to Xenforo really was the death knell for the site when it came to all the users that left. I know I missed it so much and I got way less interested in the site when that feature was gone and I run the site.
I'm on a page about incorrect corrections, and spent the better part of like two hours trying to get someone to understand that -5^2 = -25, not 25, and then that post had comments get reposted because that group is self sustaining, and that person was in turn trying to explain what I just explained to them. And I'm taking that as a victory