I'd be worried about making it farmable for soldiery as it might make dungeon queues even worse if all the tanks/healers decide to farm this instead.

So it would either need to give something that's useful, but doesn't need to be overly farmed, or if it was something like soldiery it would need to have its own cap just for that event so that people don't ignore dungeons (but not a lockout, so that way someone could still help a fellow FC member after reaching their own cap).

Otherwise it does sound like a good idea.