It would take a lot of fiddling, but since newer Jobs don't benefit at all from a Hunt Log, I think it would be neat and convenient for crafters/hunters/completionists to have a Bestiary instead of a Hunt Log.

They could get completion bonuses for both basic monsters in an area, and for finding out what everything a monster will drop(which isn't much, but it's an added bonus). Rather than working by level/tier, it would just work by region. Some regions would take beginners longer to complete, but since the Bestiary would really benefit players who are already at least 50 and working on a crafter more than the beginners, I think it would be a nice touch.