God, when I first saw this, all I could think about was Digimon! But hey, if it worked for Digimon, for the short time it was popular, why wouldn't Game Freak wanna try it too :P
I personally, love the idea! Nintendo is finally breaking out of its repetitive cycle and breaking into some new, untested grounds. Sure, who knows that the population will think of it, but I really like the effort of at least trying something kinda new. The Pokemon Amie was another thing too, I simply adore it!
Some of the forms remind me of like a godly appearance. So what if they are OP in some ways, you're only allowed one per battle anyway, so I say that it's better than having a full team of six XD Naturally, I don't play competitively. I would imagine that they'd have a tier with no Mega Pokémon and another with them, just so it gives the battlers some lei way, and to give them the same gameplay they're used too!
I love the designs and most of all, I love how some of these very underrated Pokémon have been brought back into the spotlight! Like Mawile? I loved it during gen 3, but forgot about it during my other playthroughs, but now, I totally want it again! I hope Nintendo and Game Freak will be brining some Mega forms to more underrated Pokémon like the Seedot family, or maybe even classics like the Caterpie family or even Pikachu (though I doubt they'd touch the gem of the entire series)
It's a cool idea and I think it'll do well ^^ I love how Pokémon is evolving along with the hardware and the audience (see what I did there? :P)