but the precedents in finance exist..
so if 2059 comes along and 300,000k coins from 2009 blocks never moved and you reset them back.
you do not increase the actual 21 million coins.
Using precedents as a justification for it would be a poor argument. There were plenty of practices in banking which were intentionally not adopted in Bitcoin because they are against what Bitcoin stands for. "Resetting" the coins would be one of these points.
if the announcement is made in 2049 that the recirculating of the frozen 2009 coins begins in 2059 the problem is solved if almost none of the frozen coins get moved.
It does have the problem that maybe of the 300,000 frozen 2009 coins only 50,000 are really frozen.
but the owners of those unfrozen coins can simply move them to a new address.
Why should we penalize users who are not up to date with Bitcoin? Stealing coins from someone that didn't see this "notice" would be unreasonable. Coins can also be intentionally burned; we should not be recovering those coins because that's the original intentions of the sender.
no loss of privacy And eventually the 21 million coins all get mined but with a longer delay say 2300 not 2100.
I guess tail emissions are better as they would be a longer solution.
but reclaiming frozen coins would work for at least as extra 50-125 years
This is a pretty contentious points. There are no supporting evidence that we require such schemes. Even fiat is inflationary, and we do not reclaim funds from anyone just because they don't move their cash around.