>>26956917An obvious way is you start off, in Alola, with capturing or being given a 10% Zygarde, which is explicitly said to only have one core, with the ability Aura Break, which it's shown to have as well as Power Construct like 50%. You go and find a few more cores either through also capturing them or just "obtaining" them or whatever. And this unlocks some way to change your Zygarde's ability to Power Construct. As well as a way to switch between 10% and 50%, probably, seeing as how Power Construct always goes to 100%.
This is a nice way of getting around problems when you import a Zygarde from Gen VI too. It'll still have Aura Break and can't got to 100% until you do a quest or whatever.
Who knows how we're going to see Cores in the game? They and the cells seem to be part of the power construct animations, but otherwise we've yet to see them in game at all.