...
What other requirements are there, if any? And why might they be needed?

You are misinformed about what capitalism is.
Pure capitalism is absolute freedom coupled with respect for rational property ownership. Consequently those are also the only two prerequisites you need for capitalism.
(definition of rational property ownership: ownership based in first principles supported with reason and not some illusion supported with violence)
That doesn't make sense. If the concept of property ownership is rational, presumably there's some rational
cause for it? I'm prepared to accept that property ownership might be irrational, e.g.: it's axiomatic and it "just is" or "it got made up because it's inherently true", but that's like saying that god "just is". No-one (in this thread or any of the other discussions I've seen) has ever presented a rationale for where the concept
logically comes from.