I admit, I was never a fan of the Avengers. You put Thor or Hulk next to Hawkeye, the power imbalance is just dopey, although if they 'power down' the movie version of Thor this may improve things.
You don't need to 'power down' anyone. Black Widow and Hawkeye and that are utilised when you don't want the attention of huge dudes swinging their fists, hammers, shields, and repulsor rays all over the place.
True. Although that does polarise the situations in which the characters can be useful (I mean Thor can fly, is as strong as the Hulk, can fight really well, and can control the weather). I'm not sure how restrictive that will be in a movie format. Still, Cyclops ended up being neutered in X-men in order to focus on fisticuffs so I suppose they will write in situations that will allow the lower-powered characters to show off their skills.
One of the reasons I like the Captain America comic is that it can showcase the lower powered characters like Cap, Black Widow, Hawkeye, Falcon, Nomad, Demolition Man, Diamondback etc. Sort of Batman level characters with the gimmicks spread across more characters.