You can either freeze vulnerable spend paths and let a majority of owners reclaim their coins (via seedphrase) or you can let some QC startup steal a ton of lost coins and dump them on the market, impacting everyone. This is a really obvious choice…
Discussion
Stop thinking you have a problem to solve here. Bitcoin is wild, your opinion doesn't matter (neither mine).
If (AND A BIG IF HERE) QC one day evolves to this point, whoever had their coins vulnerable will pay for being negligent and those who invested in QC to retrieve this bounty will have their pay.