But it appears not to be enough.

I'm not convinced that anyone actually did any work towards the nematode upload project. Who would fund it? I did hear recently the claim that it was tried and failed, but I haven't seen any evidence. ETA: at Nick's link, David says that there hasn't been any work since 2001. The work I saw from 2001 looked just like a proposal. He also mentions (at github) a paper from 2005 that is relevant, but not, I think, simulation.

Until it has been demonstrated in, say, C. elegans, it is so much moonshine.

Just because Markram isn't doing the obvious thing doesn't mean he is a fraud. Funding agencies and journalists aren't suspicious, so there's no incentive to work on non-sexy projects. It should make you nervous that he might fool himself, but he might not; he certainly believes he has other checks.

I heard a rumor that there has been renewed interest in the nematode upload project, but I don't have a reference. ETA: this was probably what Nick links to.

But it appears not to be enough. In view of that, what will it really take to do a whole human brain emulation? Until it has been demonstrated in, say, C. elegans, it is so much moonshine.

A lot, I expect, and yes. And I expect all sorts of difficulties to work through in the first attempts (giving rise to both ethical and existential difficulties).