Originally Posted by
Pann
In the past you used to get account bound pets in the mail when you created a new character regardless of what realm the new character was created on so it stands to reason that a similar, modified system could be used for heirlooms. We, also, have account wide achievements, pets and mounts now which I'm sure they could use as basis for account wide heirlooms
They already have systems to transfer characters and even whole guilds with full guild banks, achievements, perks and rep so I doubt it is as difficult as they claim and certainly not so difficult that a company of Blizzard's size, ability and calibre could not develop a system in over four years.