Would be an awesome idea, been wondering about that, or a transportable summoning stone (To make more people able to summon).
But again, Blizzard enjoys to bump us further downt the line. Nothing on 5.2, and nothing except a pet or two in 5.3 - I am growing more eager by the fact that we haven't gotten an update for engineers, but all others have (Except Alchemy, struggling there too).
But loooove your idea, could be cool. I already have a mini city when I pop everything.