I have got suggestion;
What about making next few enviroments? Big Boy is very easy. Just 2-3 days of active playing, and you beat him. In 2v2 is way harder. You fight 2 mechs at once, but made of legendaries, not heavily nerfed epics. 3v3 is just extreme. There are mythicals. I know, Big Boy has got one, but it is just faint. 3v3 would be same as now, because it's almost unbeatable in insane mode.
And I really want store comeback, beacause we just loved this. Your favourite cards were just waiting in store to buy. The only rarity you can't buy is divine, because it would make no sense. But when you wouldn't accept it, you can make something similiar, but this will be making [selecting the item what you want to make will cost more] card in item factory.
These are my suggestions. Thanks for reading.