I think at this point just about every non gear reward should be account wide.
Costumes (non trinket ones)
The first 3 are the most important, though, I think.
I am someone who has main changed several times. I don't really do it because I want to do it - I do it because the people I'm playing with have a need for some class or role that I can fill.http://us.battle.net/wow/en/character/anvilmar/marionette/advancedhttp://us.battle.net/wow/en/character/anvilmar/chicane/advancedhttp://us.battle.net/wow/en/character/anvilmar/ashunera/advanced
Feel free to check out, most notably, the titles/achievements/mounts on my Druid (which I have yet to play a meaningful amount this expansion), the mounts on my Death Knight, and some more mounts on my Shaman on top of all the varied achievements and feats of strength I've done.
It really kinda sucks I can't have all this stuff on my main.
I haven't tallied, but if it were all on one character, I'd have something like:
Mounts - 150 (including some extremely rare ones and a few that are now impossible to get)
Pets - 130
Achieve points - 13000.
I'd have to guess a part of the concern is that people don't necessarily want to be tracked on alts - having achievements/mounts/pets etc. showing on alts would allow people to figure out who you are, so I think any such system should include the ability to hide achievements/mounts/pets etc. on any given character, to protect privacy.
Regardless, my single biggest request for this game is to make my accomplishments and collections account wide.