What’s being sought here sounds a lot closer to “employee” or “indentured servant” or even “slave”. But it’s not a citizen.

But I don’t think the Citizen X described is a realistic one, one ever likely to be encountered in the real word in significant numbers.

America used to be populated by a majority of Citizen X types, so it’s not difficult to determine their characteristics. They should live in small towns or rural areas. They should be socially conservative and probably religious. They should have strong attachments to their immediate family and to the people in their local community. They’ll be proud of their independence and distrustful of government intrusions on it. They’ll have a good dose of what were once called “the Protestant work ethic” and “bourgeoise values”. They’ll be embarrassed by the thought of drawing public assistance and will look down on people who do so.

Such people will contribute less on average to the state than the North-East web programmer, but they’ll take far less in the long run.

And of course, citizens fill roles which are vastly more consequential than mere economic donors to the state. In those other roles, my Citizens X beat yours hands down.

should have been “does NOT exist”.

For one thing, he does exist.

What is more, he is unlikely to ever exist. In the real world, people who live in the North-East corridor and make a good living doing web programming are reliably left-wing in their politics.

This negates whatever advantages he offers by being a net plus on the treasury in his own economic life.

You don’t mention his politics at all, but that’s the persistent weakness of all efforts to analyze man as a purely economic “externality”.

Like unicorns, externalities do not exist.