This is probably going to get me trolled, but I don't care. I come from the camp that will try even if they are sure of the answer (in this case, a big fat "NO").

What I'm suggesting is that tabards given out for events that will not be repeated should be bind on account. Moving these tabards about should not give achievements or count towards achievements and should be a vanity item only on the toon it's on. Times change, people like rerolling or leveling new classes, and sometimes the saddest thing is a special tabard you can't get again.

I rerolled Horde to play with friends after playing Alliance for the longest time. My old paladin had a Argent Dawn tabard that I loved to bits. When I rerolled, I leveled a new paladin because I enjoyed the class. The possibility of faction changes mean nothing cause I've already put in a lot of work on the new paladin (who was leveled after Wrath). I'd love to have that tabard on one of my toons, but it's impossible. The fact that the old toon has the tabard is the only reason I don't delete them for space.

If faction changes come to turns, I would honestly pay for a faction change on a toon I don't actually intend to play just to get this tabard onto one of the ones I do care about. It's retarded, but that's how it is.

I really hope I'm not alone in this feeling.

TL;DR: Wah wah I made the choice to switch factions and reroll and now I want my toys on this side as well.