I think we shouldn't even have legal names anymore. Nor legal sex/gender. Why does the government even need to keep track of my name at all? Maybe we just have a number tied to our biometric data. Maybe our profile is just defined facial scans, iris scans, thumb scans, and, for ultimate proof, our DNA profile. The state has a profile number on you that ties you to your biometrics. That sounds scary, but the government already has a profile on you if you have any kind of state-issued ID. And states are already collecting biometric data on their citizens.
We could simply tie all state business to an ID number and biometric data profile. When doing a transaction with some other party, the same biometrics could be used to prove your ID. Buying beer at the store? You hand the cashier a card that has your photo and ID number on it. They can type that number in their computer, query a state database, and return your age. Opening a bank account? Prove your ID with ID card and at least two forms of biometric scan. Signing up for a mortgage? Prove your identity with a DNA test.
We don't even need legal names. Or legal genders. Let's just do everything with biometric data, photo IDs, and other methods devoid of all the cultural baggage. Let people call themselves whatever they want. Let others choose how to honor that choice.
You want to change your gender? Have at it, the state doesn't care about your sex or gender at all. It doesn't even keep track of it. Give your kid a stupid name? At any time, they can start telling their friends to call them by a different one And that new name will instantly have all the legal power as the one their parents gave them - none whatsoever. The state will no longer tell us what our names are. Our words and character will do that instead.