The sad thing is though, there were moments of brilliance in 'St. Anger', which is why it was such an unsatisfying experience. There are moments in that record that had me grinning ear to ear, thinking 'Yes! They're back!', quickly followed by the sense that they were dragging things out for too long, which would quickly nosedive into boredom. Then the next song would start, and the process would start all over again.
That was that album's failing, I think: they tried to recapture their old skill of writing long, complex metal epics that could enthrall at every turn by using the Pro Tools 'mix n' match' method. The result: a collection of miscellaneous riffs dressed up as long, complex and enthralling metal epics that were, in truth, just long. It was as if they had lost confidence in their own songwriting skills and let the computers run the show.
So, going back to the topic, I think that, for me, the appeal of Dev producing them would be the possibility that he'd be a good influence on them creatively: being the modern master of the metal epic, he could encourage them to trust their own creativity and return to an organic style of songwriting. That, and forcing Lars to put away his pot & pan collection
That is, as others have pointed out, assuming they'd let him do that. Oh well: it's fun to dream, huh?