How about an automatic (or semi automatic filter based on meta data) playlist creator, which would group things into logical collections such as series or director. For example (I did this by hand, which took a while) make Collection that contains all your Disney films, one for James Bond, Star Wars (easter egg - it only does Machete order), Studio Ghibli, Universal Monster Classics, Hammer Horror, etc. It's time consuming to do this by hand.
Collections are already in plex, although they hav to be enabled in the Movie database agent settings. The rest is also in plex, clicking on the directors name in PlexWeb will bring up all films by that director, clicking the actors name gets films by that actor,add filter of studio name gets things by that studio (e.g disney), etc.
These features seem to be being worked on still, if you look at the recently released xbox one app, they seem to have made strides in this area, just waiting for the functionality to make its way into the other plex interfaces, which hopefully will be soon as the xbox one app looks great!
Early 2021 clean-up: implemented (collections, custom filter -> smart playlist)
