The question is: is it possible to somehow destory (or maybe just hide) the attached TheDroppedRing entity?
You should be able to kill it by having the hero(es) triggering a weapon that only targets TheDroppedRing upon recieving the Upgrade_MyFancyUpgrade upgrade, and kills it instantly. You might have to adjust TheDroppedRing's health, I believe there's an InstantlyKilledBy mechanic (though I might misremember the name). You can then decide if the hero will drop a new ring upon death when it has that upgrade, which could again remove Upgrade_MyFancyUpgrade from the hero.
At least I don't see an issue with this.