Why Kill/Disable Major Characters?
The Avengers comics have been going for a long time and people love them. These movies have been going strong and there's no way another epic storyline wouldn't be successful.
People would see another Iron Man and certainly Captain America. A well made Black Widow film might do well, so why stop it all?
Characters die all the time in comics and come back, so that could easily be done here, but if not it seems like the company just did away with majorly successful characters.
Plus, it's depressing when comic characters die as superheroes represent a will to live and carry on.
Why do you think they went that direction?