I want more products filling the middle ground between complete adventures and atomic building blocks. I have monster manuals, but I want examples of well-designed encounter groups and sets of encounter groups, ideally with some narrative logic and flavor. I like the Ultimate Toolbox for its lists of role-playing seeds, but I would love collections of complete "stat blocks for roleplaying" as defined in Mearls'
latest Ruling Skill Challenges column. I like Dungeon Tiles, but I would buy examples of clever battle maps with engaging and interactive terrain (whether hand-drawn, composed of tiles, diagrammed more generally, or lavishly rendered).
I realize that I could mine all of these things from adventures, but I sometimes think it would be more efficient to consult a library of components instead of having to read and analyze so many adventures to find what I want. If I want to build an adventure where my PCs fight pirates, I want to be able to look up a collection of encounter groups for a pirate crew (I can use as many of the groups as I want, to tailor the size of the adventure), apply a role-playing stat block to the captain and his first mate both to seed the story and to flavor the NPCs, and then consult a book of battle maps for ships and harbors being raided, etc. Throw in some prewritten treasure parcels (complete with rich descriptions of ancient doubloons and the weather-control wondrous item/artifact the pirates used to power their ship), and I'd have a complete adventure, tailored to my preferences, with a fraction of the effort of assembling all the components myself.