I have a few tidbits of info about the games and some of the things surrounding it

>The new Gen 6-7 sprite for Notch-Ear Pichu isn't a mistake, rather it's recieved as an in game event after one brings over a pichu from the VC Gold and Silver games and trades it with an NPC. It is bankable this time, and the NPC mentions that "it feels like this Pokémon has been waiting a long time to meet you".
>Since it is indeed an "alternate take", the starters all have their currently unavailable hidden abilities from the get go.
>The new, weird looking Z Crystals the player is seen using sideways are directly tied to Necrozma. Said to be "chunks" of its armor left after it fell to earth, the prismatic Z crystal gives Lycanroc it's new "form" after finding the item in 10 Carat Hill (where Rockruff is found). The form is version specific, making Midday and Midnight Lycanroc have pointy black armor, and it is incredibly similar to Lunala and Solgaleo who's forms are also activated through use of a Necrozma Z Crystal. The forms last only the battle, like Ash-Greninja
>The story has to do with this as well, as it concerns Lillie failing to stop Nebby from being captured and forced to evolve into the box legend, as well as Lusamine being fixated on the prismatic chunks of Necrozma that power the legendary up in weird ways.
>There are no new ultra beasts, but they are catchable yet again in an expanded lore version of the quest with Looker. One of each Beast available in the different versions are shiny as a bonus.
>There are new Alola forms, on of them being :
A Tangela/Tangrowth that is pure grass, and looks like regular Tangela except that its vines are dripping with jet black oil. When hit with a fire type move, it's ability allows it to change form into fire type and it looks like a ball of flame with eyes. All of its moves become fire type STAB regardless of type for the remainder of the battle and it reverts when it's over.