I think this Frogadier will help the viability Greninja BREAK, as it saves you from taking up 3 spaces in your deck for Froakie. Of course, that still means 13 spaces if you want to run 4 Greninja BREAK cards, and you'll also need some other basics for your first draw odds. Of course, a full run of strong basic EX cards (or weak ones if you like Emolga EX) only takes up 4 spaces in a deck. Multi-stagers still need a lot of help to compete with that (beyond the 2-prize rule).