Yeah, I'm lifting concepts from several sources and trying to keep the scale large enough that even extremely powerful characters will be unable to overcome it easily. I thought Hickman did a great job with this sort of thing in his work on the Marvel Comics event Infinity where everyone had a role to play. Folks like Hawkeye, Black Widow and Captain America flew spacecraft, or fought against footsoldiers on crucial special ops style missions, while characters like Captain Marvel and Thor flew alongside the fleets and engaged giant spacecraft one-on-one.
To stop things like time-travel and the like, I was thinking of putting some Lovecraftian/New Gods element in play where the mere presence of the Invaders alters the reality around them and makes certain abilities and spells impossible or backfire spectacularly.