Doesn't seem to be a good idea to lock unused Bitcoins. If someone is just saving it for some reason, they can lose them. And it doesn't solve the addresses with large amounts of Bitcoin. They can just move them every one or ten years to another address.
To determine the price of one BTC you don't have to know the total supply. It's always a matter of supply and demand.
That's the point. Forcing them to move them would produce proof that the coins are active. And I would argue that to make supply and demand work (correctly) you need to know the supply.
But I guess taking the chance in losing at least ten percent (at least, probably a lot more due to the uncertainty) of the total value of the rest of the coins when the Satoshi coins move are the preferred sentiment on this forum.