When I think of how a Marvel's Elseworld's could be, it would be more about adapting some classic Comicbook storylines into films which didn't or don't fit into the MCU continuity , or that can't or won't be adapted into the continuity.
I would see them as
one shots, as opposed to a whole separate ,ongoing continuity, like
The Batman part 1 and 2.
They could even do them as period pieces, which would further distinguish them from the main MCU much like
Joker was set in 1980.
An Example would be something like the Tim Sale color adaptations like
Spiderman Blue, and
Daredevil Yellow which have that 1960s type setting and feel
Yes, I know Spiderman is owned by Sony, but I'm just using these as examples as the type of " out of MCU continuity" stories they could do for an Elseworlds tale.
They could even do something like the Alex Ross Classic
Marvels , which was from the perspective of a man on the street of these characters though the decades
They could also have to feature new actors as opposed to getting Chris Evans back to play a different Steve Rogers.
That's how I would see it at least.