Possible? Yes, but it's a metric fuckton of work that the devs won't do and most of the playerbase doesn't want. Please consider playing cartridge games if you love Gen 6 so much.
>be new player
>upset I can't steamroll each battle
>become friends with endgame player
>travel in party together
>he finishes each battle for me
>never need to put any effort in
Not to mention the amount of work to go back and rework NPCs AGAIN just so they have code for co-op battles.
Megas can be implemented in the Gen 5 engine and older engines, see the mega moemon thread and various BW/BW2 hacks that contain megas. So not only are you wrong, you're an asshole too.