while comics are a refernce for the movies and sometimes even do some R&D I don't think his Avengers appearances are a measuring stick for anything. I think writters had storries to tell and he fit what they wanted. Remember like 10+ years ago when 616 and the Ultimate Universe both had vampire events featuring Blade, because both writers conicidentally wanted to tell teh same story at the same time. (The Ultimate story wa sbetter just fyi).
Al Ewing had Blade in Mighty Avengers for what two or 3 arcs, because he fit the story he wanted to tell.
I know Tom Brevoort was trying to get Blade on teh Avengers for years, but it never worked out for one way or another. I like your enthusiasm about everything, but I don't see how Blad fits unless they want to pull the Avengers into a big supernatural story line right from th ejump. Introduce Blade first and let them establish him.
I don't see how BP and Captain Marvel are too big for the Avengers if anything they are the strongest foundaitn for the team. Cap's retired, Tony and Natasha are dead. Those are the biggest draws. Besides Avengers only deals with world ending or universe ending threats. It could be Galacatus, Kang the Conqueror etc. BP's been a long time Avengers staple I don't see how that would change. He's not gonna be runnign down bank robbers in NYC, but for a global or Universal threat the MCU has positionined BP to be involved and take a lead.
Marvel's clearly positioned Captain Marvel to help out with the Avengers and basically established her as a Superman type character.
Marvel usually likes to introduce characters and build things up. They've pretty much ignored all the TV stuff to the point where you wonder if its even canon. You'd have to introduce Ghost Rider and a lot of other things. You can't just plop Damnation or Midnight Suns on the Avengers. Also Dr. Strange is the only one that's alreay introduced who really fits in a heavily supernatural story. Sure it could be done but the other characters are more general superheroics and sci-fi