You can do that right now in every modern socialist country, but what about the USSR and the Warsaw Pact? And any future socialist and communist experiment(s)?
By self-employment, I'm indeed referring to running your own business, but I'm referring to a sole proprietorship or freelancing, not your typical business where other workers are exploited for the benefit of the owner.
It is worker’s ownership of the means of production. If it grew the new people would just have to be cooperative owners. Iirc Gaddafi advocated for such socialist entrepreneurialism in the second section of the green book.