What about a voting system? With little keychains given out with only the voting system having the public key for, and any third party can validate the votes. "Coins", or voting credits can be distributed back to voters without transaction fees.
It has the same problem of every cryptographic (and not cryptographic - see paper) voting system. It's impossible to create a system that assures both a correct result and voter anonymity.
Paper assures none, but has quite strong guarantees on both. I'd settle on some system that assures the result, and has good guarantees of anonymity, what one can create with pseudonyms, but at that point it's a political debate, not a technical one.
People don't have to share their name to their public key in the blockchain. So the anonymity is about the same as a social security number, and but confirming the identity is much stronger and doesn't need to reveal private information or their private voter's token keychain. Transparency is giving out tokens to known voters, since there is already registration at least in united states elections. What it does give is a strict list of keys that should correlate with registered population.
"Now, the voter makes his vote. He generate a nonce (unique number used once), makes his vote, signs it with his keypair, and encrypts this with the public SMPC key. ... Since the vote wasn't encrypted with the voter's key, he can't decrypt it which means that nobody can prove what he voted for using the encrypted message."
Eh, he didn't encrypt it, but he signed it. How can people not prove that he created it? Whoever holds the SMPC key knows everybody's votes.
Bitcoin as a store of value is only when people are holding other commodities or speculative fiat. Large caches of early bitcoin holders will likely not crash a market that creates them wealth, so if there are actual commodities that align with bitcoin, and illegal drugs are not that commodity for a multitude of reasons and even just fluctuated with the usd, so bitcoin either needs significant natural resource or "hard assets" backings of bitcoin or it'll ebb and flow with the USD because shops that accept bitcoin still have to pay to do USD conversion and the rate moves dynamically just like there is a broadcasting network for the gas prices for gas stations when the gas price per gallon fluctuates quickly based on futures markets.
