I completely agree with your list. These are much under appreciated Avengers. Seeing as how there is a new female Captain Marvel I really wish Monica Rambeau could take a much more prominent roll on the Avengers or in the Marvel Universe in general.
I personally hate it when creators try to push their own political beliefs or agendas to the forefront. It should be about the characters not who happens to be writing the characters at that moment. DC drop the ball this time.
I love the character Viper. She was one of Captain America's greatest villains, sadly not the character has been hijacked more and more into being a X-men/Wolverine villain. She was always a portrayed best as a crazy psychopath with zero regard for innocent lives. I love it how back in the day the would only show one side of her face. It gave the character a certain mystique, sadly that is gone and now you see her full face all the time.
I would love to she her play a big role once again. She really is awesome a a psychotic terrorist. I prefer her on her own rather than working with Hydra. She should be a big time Marvel A-list villain.
I still hate the Isaiah Bradley retcon. It literally drives me nuts when Marvel does this it to me waters down the mythos created. I generally not a fan of retcons in general but have recently enjoy Marvel Project and the Winter Solider retcon.
John Walker is my favorite substitute Cap. I can't believe Marvel can't think of anything better to do with him than just have him as a cripple running the Raft.
I would love to seen William Burnside resume his Grand Director role. His character is nuts and is a great Cap villain.