How does taking 5000 gold out of circulation sound? Would that be OK? Because that's the amount they've got on them right now, that will vanish entirely when they autopause.
That's the tip of the iceberg.
You can't deduct gold from a realm. You an only deduct gold from characters. Doing that would entail removing gold from players who haven't done anything wrong. We don't punish players who haven't done anything wrong.
Can you track what regions they put investments in? If so can you reduce their yield for a certain amount of time?
