The amount of revenue gained in a near 100% system would guarantee basic income for all, including children. This is my point. Take away gifting and nepotism and automatically assign an equal amount of potential resources to each child from birth.
You can't take away gifting unless you take away private property - how you can prevent me spending my resources (no matter how much/little of them I may have) on rising my kids instead of myself?
The natural unit of the economy isn't a person, it's the household - all the legislation and market theory is about resource flows between households, we've never had societies that were able (or even intending) to control resource flows within a household. The only way to ensure equal resources to each child from birth would involve also fully centralizing childcare - i.e., taking them away from parents and raising them all equally by some single anonymous system; but I'd call that a dystopia.
I do want my children to have an advantage in resources if I can help it, it's a natural property of homo sapiens and most other mammals to care about their offspring.
You can take away 'nepotism' in that sense as soon as you're able to genetically modify our species to have a different psychology than homo sapiens - and while we're at it, this could also solve wars, greed and a bunch of other problems.
Implementing what you propose might be possible, but it would require to apply violent force on a mass scale, as almost all people would naturally want to circumvent the system at some point and need to be forcibly prevented from that - or it all goes back to the "communism" where in theory everybody is equal but in practice it's just empty words and everybody cheats the system.
