Well, in reality the productivity gains usually go to the owners of the means of production, not labour. So if Sweden only required one person to actually perform labour, then that person would get paid a high salary, but the owners of the company doing that work would get all the profit, and you would have to tax them somehow. And
they would do all they could to evade taxes.
So to reach that limit example, you would have both productivity concentration, and an enormous amount of capital concentration in the background, screwing things up, making it harder to reason about the example.
I think Blockbuster vs. Netflix is a very good illustration of what happens when productivity concentrates. With Blockbuster, you had 300k simple low-wage jobs. But they were distributed across the country, so their collective income taxes were also distributed into a lot of local economies, doing good locally.
Blockbuster went bankrupt, and Netflix took their place. So instead of 300k distributed low-wage jobs, you now have 10k high-skill high-wage jobs, but they're concentrated to LA and Silicon Valley. Those employees pay local taxes there, and nowhere else. So from a national perspective, you now need to re-distribute those taxes to the areas who lost tax revenue, somehow, without pissing off the employees, and without pissing off Netflix, and without pissing off the local government in SF and LA. Usually this is done through federal aid/job aid programmes that take money from richer states and distribute to poorer states, but that's an incredibly blunt instrument.
But if you were to tax productivity and if you were able to tax it locally where it's consumed, this change from Blockbuster to Netflix wouldn't have disrupted local economies. Because then it wouldn't matter how many employees did the actual production, or where they were located, and that's good for the places that productivity is concentrated away from.
(Unless, of course, you are of the position that fuck those guys for living in the middle of nowhere, they should move to the cities like everyone else.)
Anyway, tying it all back to the original point, productivity concentration necessitates some kind of new/stronger redistribution mechanism so the gains are spread across the entire population. Previously, and still, when we have income-tax and a high percentage of the population participating in the labour force, that distribution happens automatically.
Maybe a productivity tax to make sure the country as a whole captures part of the GDP, UBI to spread it equally across the population, and then local consumption taxes to redistribute to local governments? I don't know.