How to address coins are "lost"?
Whenever you access your wallet, a 10 year timer will begin/reset. If the wallet is not accessed again in 10 years the coins will go back to the mine. Keep in mind, i never mentioned activity (sending or receiving), simply accessing, or logging on.
It's Bitcoin, not a domain renewal, you know.
Also, that approach, to recycle lost coins into mining process, is absolutely wrong and devastating. Imagine, I have a wallet where I hodl bitcoins. 8 years have passed and somehow bad thing happened to me, I got into a coma or was arrested for political reasons or etc. Let's assume I got wrongly convicted of attempting a crime. I spent 4 years in prison and then they freed me. What happens when I go outside? My wealth, my bitcoins, are lost.
Also, radical changes like that, will finally bring bad power. If people feel okay to do such a huge changes, then I'm afraid a dictatorship will slowly take over bitcoin. At first we set 10 years, then 5 years, then someone will come up with an idea to recycle all bitcoin wallets that don't come from exchange and aren't KYC verified.
Just leave things the way they are, there is no need of such a change at the moment.