Far from being the same thing, but are you already using the theme component that allows you to search for GIFs and insert them when composing a post?
As far as I understood from Pandlr’s “GIF Pocket”, it allows you to have a list of favorite GIFs per user, is that right?
I ask because with a solution similar to Watched Words, only admins could define automatic replacement terms, it wouldn’t be a per-user archive.