So I've got to wonder if we should look at him from a more limited stand point. His role might be the "world-eater" or even a homologue of Akatosh, but he still might in practice just be a super ancient super powerful dragon. By this, I mean his literal and direct world/time-changing powers are somewhat limited, and so maybe his goal is to bring back enough dragons/servants to assail and finish off all the towers. And from this he might "end time" by whatever would happen. That at least seems the more intuitive suggestion to me given what we saw of him and the dragons in general in-game.
Of course though... it really could be Bethesda just not paying attention to itself....