I would like it if Playlists and Smartlists could have all of the same Customize View options as other View Schemes, including adding View Categories (such as Genre, Season, and Artist) and being able to show and use in Panes/Tiles filtering mechanisms.
As it is, I don't use the Smartlist functionality in MC, preferring to keep these types of "radio-station-like smartlists in a "Mixes" sub-views of my Audio hierarchy. I do this so that I can have the option of using Genre/Artist/Album panes above the auto-generated list of songs for subfiltering purposes.
However, this creates some problems. I'm not able to use these lists as an easy basis for auto-filling my handheld devices. You can choose from your Playlists, but not your View Schemes. It also forces me to manually import and recreate these views in Theater View (and then WebRemote view too), whereas it would be easier just to add the whole Playlist subcategory (which shows all the Playlists and automatically deals with "folders" nicely). It dawns on me that moving these functions back to the Playlists part of the tree, where JRiver seems to think they belong, would be actually quite helpful. However, I really LIKE the ability to subfilter my lists. It would even be cool to be able to subfilter my manually-created playlists with panes, on occasion.
So, would it be cool to have the full Customize View dialog for Smartlists and Playlists too? If you just add a new Playlist, it could work just like it does now (showing no panes or anything) until and unless you go in there and manually choose Customize View and add the Categories in, after which the Panes and Details combobox would "light up" and let you configure that stuff as well.