We would like to share an insight on the approach that is the philosophy behind the heirlooms at the moment. This is still something that may change, so please do not take it as set in stone.
In short, the developers agree that the process of mailing heirlooms around constantly is a little annoying. We'd prefer to try and work ourselves away from the method of mailing out BoA items in the future, like pets, mounts, etc. To that end, we have some design goals in mind that would improve this sort of item distribution system. And with those design goals have come some ideas for changing heirloom mechanics. This is sort of contrary to the idea that was shared in the past about just designing the system to allow players to mail their heirlooms all around their accounts without realm restrictions.
That's all of the information we can share at the moment, but we feel like it's worth pointing out that the design philosophy we shared earlier isn't so set in stone -- we're reevaluating these types of systems as we look toward the future. World of Warcraft is a living evolving world, and so the systems and mechanics that make it possible.
We have an update to share regarding the prices for Void Storage. Instead of charging 1000g to unlock a Void Storage vault and 100g to deposit and withdraw items, we're looking at only requiring the following amounts for each transaction:
Unlock - 100g
Deposit - 25g
Withdrawal - Free
We agree with the suggestions we've seen that placing a higher fee on withdrawals would create a stronger deterrent for using Void Storage as a secondary bank. That said, we don't want players to find themselves in a situation where they are unable to retrieve an item simply because they don't have the gold. This is why we're leaning towards a more expensive deposit (to differentiate Void Storage from a normal bank) and allowing all withdrawals to be free.
Please keep in mind that these prices may not hit the PTR and are, of course, subject to change before the release of 4.3.