Best I can tell, all of the problems you cite are fixed by MacRuby. It shows how surprising well Ruby semantics maps onto the message passing semantics of Objective C. They also found ways to wrap up the C stuff without making you manage your own memory.

Not sure why Apple hasn't been more aggressive in pushing it for Cocoa development. Maybe because they don't trust it to perform well, yet, on iOS devices and don't want to promote it until it can be used anywhere as a replacement for Objective C.