Well, first of all your example makes it hard to tell if you're describing a percentage-based attack (i.e. 51% attack or 34% attack etc) or a long range attack.
In your example, how much % the currency are you claiming a thief has stolen? Are you saying you're using private keys to rewrite history that is based on staking deposits that predate recent chain synchronizations by the node who's view of the history is being compromised? I can respond better if I understand what you're trying to say.