All of the above = a huge bag of hurt that presents some damn near insurmountable problems (leadership, on its own, is a huge issue).
To be honest, I don't know how one would get past those things without first deciding, with a clear conscience, to hijack Ruby from Matz. I know that sounds malicious, but even Dave Thomas is calling for a fork of the language. Seems to me that forking is not quite what we need, as it keeps the language rooted in the past, bringing the performance baggage with it (you're still having to re-implement the loose idea of the Ruby spec, which as you pointed out, presents some really hard problems).
No, maybe we need someone smart, loud, and with balls big enough to arbitrate their way through whatever gray areas are left with Ruby's loose idea of a spec, perhaps make some tough calls on what language features can reasonably be supported, decide what needs to be cut, and break compatibility with existing Ruby code if necessary. To top it off? This person forms a foundation around it, a la Python.org, to ensure that the language is left in good hands, gets proper funding for new development, patches, etc (hell, I would love to donate to Ruby development if I knew the money would be put to good use. I don't have that confidence now).
Of course, what I'm talking about now is not Ruby, but a new thing. This new thing could be quite awesome. Whatever this new thing would be is still years out, even if someone decided today that they would do it.
Python in the meantime?