Hunter has two really good one drops. This is probably the lowest barrier quest to finish, since you're just doing the thing you do in hearthstone, but losing that first turn tempo in the tempoest class is a bummer.
People think summoning 20 minions is hard when the current expansion's hunter has cards like halaziel(Though probably too slow), unleash the hounds, sn1psn4p, and bomb minions and plenty of other deathrattles that summon microbots and such. Remember, it's not play minions, it's summon which is significantly easier.
It's not that the summoning condition will be hard, it'll probably easy to build. It's just if this deck would be worth doing over current mech hunter that matters.
Whether or not it's playable is irrelevant, it's incredibly boring design wise. It turns Hunter into a worse Token Druid since contrary to the latter which can close the game early, you have to wait the late game when you have likely no minions left to buff to do something. Why would they save this for the reveal stream is beyond me. Not to mention that the baseline hero power of Hunter is probably a better tool to close a game. What a disappointment.