Rather than doubling all income one option would be to make the existing income more evenly spread out.
For instance McDonalds' CEO makes ~$20 million a year[0] and they paid out $6.6/share with 726M shares[1] to parasite shareholders[2] while the average non-CEO employee makes $25k a year[3].
Since there are 150000 employees working for McDonalds that means lowering the CEO salary to $200k and eliminating shareholder payouts would free up close to $5 billion/year.
If that $5 billion were distributed evenly to all employees they would take in an additional $33k/year, more than doubling their salaries.
Of course all these numbers are estimates and there are caveats but the overall point is there's a lot of money out there that's going to a very few people.
0: https://www.restaurantbusinessonline.com/financing/mcdonalds...
1: https://www.macrotrends.net/stocks/charts/MCD/mcdonalds/shar...
2: https://finance.yahoo.com/news/income-investors-know-mcdonal...
3: https://www.zippia.com/mcdonald-s-careers-7238/salary/