Or perhaps systemless instead.
Although, if we create one-page additions using one another's specific systems, we may have something with more collectible value. That is, it's for our own games, so we are far more inclined to keep it indefinitely. Something generic posted on the web somewhere may have merit on its own, but a Kumakami original one-page add-on for Midian is something I'm going to put in the permanent archives and want to show off to everyone.
Collectively agree on a licensing setup that allows reposting and derivative works (several Creative Commons licenses work). Then we just get fancy with the idea. One person could create a signature work, and retool it for different systems and settings. To use some popular (albeit non-free) game systems for examples, one could create a character named Mandy Lee and describe her as:
Class: Adept
HP: 12
or
OCC: Warlock (water)
HP: 12 SDC: 30
or
Clan: Tremere
Generation: 13th
Of course, the above game mechanics are greatly abbreviated. I would make a copy of this character for each recipient, assuming that D&D, et al. were people on these boards. Instead of different characters, locations, organisations, items, NPC's, plot hooks, or any number of other add-ons, each redone for a given recipient.