e.g more than 10 yrs inactivity 50% can be mined again 50% put in escrow for future claims.
Perhaps I have not made myself clear. What you propose is simple theft. If I want to save my XBT, and bequeath them to my great-great-grandchildren, it's none of your damn business.
I did understand and you have the unquestionable right to bequeath many years in the future. That right should be protected and the mechanism suggested is that your right would be protected from the 50% in escrow which would be used to pay any similar circumstance. At the same time it addresses the problem of those accounts that are really lost for ever.
I am not saying this is the solution but is a point of discussion to solve the problem of coins in lost wallets affecting supply substantially over many years.