1. Coins haven't been spent doesn't mean it's lost (even though some of them are), maybe the owner simply hold the bitcoin for long-term investment.
2. Why would we eliminate satoshi's stats or force satoshi to move the bitcoin? It's contradiction with bitcoin goal.
3. It would take some computational power just to find unspent coins and add it for future circulation
4. I don't see the connection between unspent coins become mined after few years and limiting block size/allowing much more tx/second.
5. I don't think it's good scaling idea since your idea require more computational power and more time to develop/test the idea without much result. Even change max bitcoin supply or add "annual return" feature is slightly better idea.
CMIIW.
The first two points are the most important... Bitcoin exists as a decentralised payment system without central authority.
If we would "steal" satoshi's coins (or at least, add the value of the unspent outputs we THINK are satoshi's to the block reward), it would be a very bad precedense.
From then on out, your balance would never be safe again... If we, as a community, did this (even once), what would stop us from voiding the unspent outputs belonging to a central bank, or maybe steal the unspent outputs from all addresses we believe are BTC hoarders?