I think this would be too limiting for humans, and not effective for bots.
As a human, unless you know the person in real life, what’s the incentive to approve them, if there’s a chance you could be banned for their bad behavior?
As a bot creator, you can still achieve exponential growth - every time you create a new bot, you have a new approver, so you go from 1 -> 2 -> 4 -> 8. Even if, on average, you had to wait a week between approvals, in 25 weeks (less that half a year), you could have over 33 million accounts. Even if you play it safe, and don’t generate/approve the maximal accounts every week, you’d still have hundreds of thousands to millions in a matter of weeks.