I am interested in tracking "inactive", "stale", "lost" coins in the block chain. For the sake of discussion, I will just call them "dead".
You can call them whatever you want, doesn't change the fact that your idea is theft
Over the _very_ long term, they are a problem. Their existence in the block chain increases the computational cost without a commiserate increase in monetary supply. Yes, BTC are divisible down to insanely small amounts now and that can be increased with future computational tweaks yet still, why have 10% of your computational load be supporting dead coins that are unusable?
AFAIK if the coins don't move then there is no extra load (except maybe on a first download of the blockchain, or a rescan... but reclaiming the coins won't do anything for that)
The idea of declaring a coin "dead" is contentious. My definition of a "dead" coin might be someone else's idea of multi-generational wealth transfer. While I would consider 50+ years of inactivity to be sufficient to declare a coin dead, others might reasonably argue for 10 years or even 1000.
If we could agree on how long to wait before declaring a coin "dead", the next question is what, if anything, should be done about it.
Personally, I would support using them to continue to fund the block chain. This keeps the miners working which supports the entire currency and it is a known, reasonable way of adding currency to the monetary system.
The challenge is reaching some agreement on what a dead coin looks like.
there will never be an agreement on what a dead/stale/lost coin is, if you take it, it is theft Even after 5000 years
Even if there was a magic number that everyone agreed to, no one would agree to changing the rules of the network years after it was started.
The good news is we don't need to worry about finding a way to keep the miners happy until 2140. That makes a 100 year time limit for that dead coin seem pretty reasonable.
We don't need to worry, transaction fees will be plenty to keep miners happy past 2140 and beyond, apart from that there will be businesses that mine themselves not for profit but to secure the profits they make off the blockchain.