Okay, I already put out my idea for how to reshape the tutorial and UI of the game to be newbie friendly which I found out was already being discussed here.
Now I am here to drop the idea about story for CI6 and then some raid idea for CIU.
Chicken Invaders VI: The Fork Awakens
"You’ve defeated the flagship of the Henpire, the Henterprise, and you defeated the Henperor’s apprentice, but you never faced the actual Henperor who now found a way how to get around you: He used the combination of dark magic and science to activate a black hole that sends chickens back in time to reach Earth before YOU were born, so they can easily destroy it without you standing in their way. But the black hole is imperfect - to reach that timeline, they have to jump between previous timelines one by one to reach the exact moment which gives you enough time to stop them.
Travel back in time through the most iconic moments of your career to face new variety of timejump chickens in alternated versions of previous waves and bosses, combined with all-new prehistoric, medieval and post-apocalyptic timelines all over the known space."
I was heavily inspired by the original name of Chicken Invaders 5, which was Paradoxical Paradox, based on the name of unexisting page which yeah, was not the official title, but the premise of going through time and space is something very current as we had Avengers: Endgame and the end of Star Wars saga both of which could be made fun of in the newest entry.
And now to a less off-topic idea:
How to incorporate co-op into CI Universe? Add raids, it’s a MMO, so raids should be “a must” so to speak. Raids would be these endgame missions in style of every last mission from previous game where you had toughest combinations of waves and enemies with the final boss. These missions would require fireteam of 4 players because of raised difficulty, and bosses would have some simple puzzle mechanics tied to them that you have to go through before you can deal damage, and it would require cooperation between players for that. But all those bosses and raids would need to be built from ground up as new, and not just rehash of previous entries.