Oh, it's perfectly workable. Split the forum in two, inform everyone they have 90 days to comply, lock their threads and threaten to delete them if they don't categorize them in time. Perfectly workable.
It's just that the most likely consequence is that the entire community rises up as one and tars and feathers the fool who suggested it for being a presumptuous ass, is all.
(Okay, okay, more likely everyone just says "screw you" and goes somewhere else, thus killing the Roll Call forum permanently.)