No way to assign Avengers keyword currently.

Shrinking will make you tiny up until the moment you are removed from the battlefield, at which point you will grow back to regular size and be forcefully ejected.

Think we'll see a Nick Fury with a power like the Legion Founders for "Welcome to the Avengers Initiative"

I would assume that would be covered by this entry in the main rule book on the definition of Ignore:

If a power or game effect is treated as not existing you obviously are unable to use it.