Could be done, would require some significant reorganization of the art board as it currently exists. Not sure how effective it would be, and it'd require a bit of work from the local mods to make sure it all works right. It also wouldn't work for significantly older threads, since I doubt anyone wants to go and appropriately re-tag those. But it could be done.
Would need to check the feasibility of doing it with the local moderators, and it'd likely be a bit experimental. We'd also need an exhaustive list of every tag that anybody might want to use, which is the other issue for a system like this.