I get the strategy behind this and it makes sense, but it's all based upon chance. Chance you don't start with hoopa as active, chance you hit your max elixirs and chance that you get lucky on the rolls. Not saying this cant work, but like you said, you have to be explosive and go all out T1. I've never tried this before so I can't say for sure how easy it is to accomplish, but I can see it working, if a little luck is on your side.
of course starting with Hoopa ex is not ideal, but unlike other decks that you got to dig for the one of Az, or 1-2 of float stone, all you need for free retreat is a water energy and a Manaphy ex on bench. the water energy attachment does seem like a waste on Hoopa ex, but the 3 energy switches gurantee you in getting back the energy to your attackers later, if not the same turn.
this deck plays 12 water energy (some play 11), so max elixir successful rate should be high, when my opponent mad at my continous max elixir attachment, they just don't realize how many basic energy i played. that's deck structuring mostly, with a bit lucki would say.
this deck requires a good understanding of the meta. on the first turn when your opponent reveal his starter (assume its not a lone shaymin ex or hoopa ex), you should plan for setting up which pokemon and discarding which. e.g. when you face Toad/Tina, set Regice with sufficient energy on it (hammer!), you win; when you see a combee. set Glacen ex as chance of they play a heavy base hitter is low; when you see a froakie, set articuno, try to get 4 prizes from it before a greninja comes out.
just my 2 cents