OK, so I tried working with ~/Library/Preferences/com.apple.recentitems.plist.
It looks like both apps and docs have a small section, each starts with about 9 lines that aren't human-readable under the key doc-aliases and app-aliases, beneath each is a section that is human-readable. keys: apps and docs.
I tried editing out sets of aliases and associated documents, but the changes don't show in the interface. Any ideas about what needs to happen to make my changes "take" after the edit?