This goes against the philosophy of Bitcoin. Forfeiture of assets shouldn't be an option even if it has never been touched or stayed dormant for the past century. There is also a problem with an arbitrary threshold where there isn't a good way to determine how long the coin should stay dormant before being recirculated. This would pose far too much of an issue in terms of both implementation and motivation. Even if you start to recycle OP_Return outputs, the purpose of sending them by the original owner would be defeated.

Between this and implementing a tail emission of sorts, I'd support tail emission. There shouldn't be a scenario where an asset gets confiscated because it lays dormant.