At first, I was not expecting Namor to be part ofAvengers: Doomsday.
After the initial shock, I rememberedNamor’s role in the comics' Secret Wars.
However, the other characters decided that what they were doing was wrong.
Custom image by César García
The connection to the comics is the first major aspect.
Wakanda Foreverended with Namor and Shuri finding a way towards a truce, with their nations becoming friendly.
That is precisely why I believe that Namor joining Doctor Doom would work so well.
Custom Image by Kai Young