Ah, I always thought Debian's efforts on this could have been better concentrated on something else. Now they are at it again.
I didn't find discussions about the effort on Google, so I have no idea how much work went into this, but if I were to decide where to invest say 200 hours of work, I would have made Bash standard and then try to improve on whatever performance problems it might have. But they rather had this as a release goal, had discussion threads on it, opened bugs and who knows how many scripts where modified, for an improvement a majority of users won't feel (I sure didn't notice the difference, whatever that might be; but I did waste time with dpkg-reconfigure to test this). I'm pretty sure Bash is not unfixable, it is a damn console, not the entire kernel.