Proof of SuicidalIt might be interesting to have coins commit "suicide" when the wallet is NOT online! Like an inverse PoS. Suicide rate would be a fixed percentage of the wallet's amount, like 0.1% each time. I'm not a blockchain programmer so I don't know how difficult this would be.
What is required is:
1) Each wallet keeps track of which addresses hold how many coins, excluding empty addresses.
2) A decentralized method to agree on one non-empty address (like the PoS mechanism).
(Alternatively, agree on any valid address and if its value is zero, nobody loses coins)
If the address agreed on can proof it is online right now by signature (like PoS), it can insert a veto and won't lose any coins. If it is not online, it will be agreed that 0.1% of that addresses coins will
commit suicide and be subtracted from the wallet's balance.
This creates a balance between a number desirable objectives:
1) Spending coins in order to not lose them.
2) Keeping the wallet online in order to support the network.
3) Working against inflation to keep the price high even if people are mining
4) If mining gets harder, the value will increase even more because the amount of coins reduces.
The metaphor would be, if one wallet is able to veto, it is still "alive", but probably
suicidal. If it does not reply, it committed suicide so that's what we write into the blockchain.

That's it basically, feedback is welcome.
would be easier to do via input age, and every 24 hours, wallets would send coins (either by individual input, or by all in address) to itself . (fee free ofc)
it would make more sense to combine all coins in a single address unless you decide to integrate PoS and depend on inputs for network security.
plausibly similar to PoS, where minting is responsible for this with perhaps a small % gain.
if coin age is over 7 days, it will deduct 10% for each day over ??
ofc, the difficult bit will be monitoring aged coins.
Frei Coin has some method to do similar with coins over a certain age are taxed.
Unlike Bitcoin, Freicoin has a demurrage fee that ensures its circulation and bearers of the currency pay this fee automatically. This demurrage fee was proposed by Silvio Gesell to eliminate the privileged position held by money compared with capital goods, which is the underlying cause of the boom/bust business cycle and the entrenchment of the financial elite, and has been tested several times with positive results.
http://freico.inDemurrage is the cost associated with owning or holding currency over a given period. It is sometimes referred to as a carrying cost of money. For commodity money such as gold, demurrage is the cost of storing and securing the gold. For paper currency, it can take the form of a periodic tax, such as a stamp tax, on currency holdings. Demurrage is sometimes cited as economically advantageous, usually in the context of complementary currency systems.
https://en.wikipedia.org/wiki/Demurrage_(currency)
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question is how exchanges deal with it.
cold wallets would be taxed mercilessly,
perhaps you could integrate veto "keys", where a wallet could use that key in transactions to remove tax.
this would be a form of centralisation though as the keys would be distributed by the dev, and for long term security would need to be updated semi-regularly to prevent illegal use of those through sharing.
but, given the voting process for other chains requires also dev intervention, this will not necessarily be a problem.