I have a suggestion, and I'd like the community's thoughts.It is well known that many bitcoins are no longer accessible due to loss of private keys, but no one knows how much. While estimates exist, they rely on imprecise methods. Most famously, there is still a large amount of bitcoin in Satoshi's wallet, and it is unclear whether they will ever be spent. This phenomenon causes undesirable uncertainty in the market, undercuts the slogan "there will eventually be ~21 million bitcoins", and in a sense causes deflation.
I thought of a way to increase transparency as to how many bitcoins are actually in circulation, and also increase miners' rewards, through a process that somewhat resembles erosion (hence the name). Seems to me it can be implemented as a soft-fork, though I haven't worked out the details to verify this (I'd like to hear what the community thinks about this idea before delving in more deeply, if ever).
Onto the idea itself. I'll make up some parameters as an example. Basically, from the moment an address receives funds, a countdown begins. Whatever funds are left in the address after 3 year will start eroding, meaning that every week from then on another 0.1% of the amount in that address may be taken by the miner (technically each block will contain a list of addresses with the funds that were taken).
If you have funds sitting in an address and you don't want them to erode, all you have to do is spend them to yourself once every 3 years. Hot wallets can automate this, and cold wallets can warn you to do this manually. Even if you forget, assuming you at least check once in a while that your funds are in place, you would see the erosion that began, and take action before much damage took place.
Although I don't think it's technically possible to include these eroded funds in the coinbase transaction itself (as that would make it a hard-fork), they could be implemented to act as if they were, i.e. they must mature 100 blocks before being spendable.
So to reiterate, we gain (a) transparency as to how many bitcoins are in circulation, since users are incentivized to prove that they still possess their private key every once in a while, and (b) miners will be able to access lost funds, returning them into circulation and increasing the security of the network.
I go into a bit more detail here to those interested: https://gist.github.com/yotamDvir/e7ff52a34460f3c9a6bf3051b0e51414.