While I do not advocate for a state-based model, I want to point out that the soviets beat the USA to orbit on a centrally planned economy. I see no reason to assume we cannot have machine tools and other high end equipment. Especially because:
> open-source is parasitic to the capitalist economy
A parasite harms the host. Open source is symbiotic with the capitalist economy. I do fully expect that these machines will be built by products of the capitalist system at first. The point is that over time these people would rely less and less on the capitalist system for directly meeting their needs. Over time if this works it would behoove them to replace the entire economy they rely on with one they control. But there are first order needs like food and clothing and then there are second order needs like parts for the machine that brings them food. They can gain a lot of freedom by just covering their first order needs with machines they own.
As far as engineering, yes my examples all center around engineering because I am an engineer speaking mostly to other engineers here. But there are other people: therapists, grief counselors, teachers, doctors, librarians, carpenters, etc who would love to provide those services to friends for free if their survival was ensured.
I am imagining communities inside of the USA which simply trade with one another instead of buying from capitalist corporations. So only people who want this lifestyle would actually choose to live there. People who are super selfish and don't want to help anyone can simply keep living in the capitalist world, and see what it's like when no one cares for anyone else.