Absofreakinlutely! He and Hawkeye are my favourite Avengers. I'm not really interested in seeing Pym as Ant Man though - only as Giant Man. We don't need to negate the use of the Wasp, and the Giant Man concept when they came out with it was really clever.
Personality-wise, I don;t want the manic depressive Pym, or the pill popping Pym, or the wife beating Pym. I want the slightly insecure, but not neurotic like Ultimate Banner Pym. Norton did a fine job of not making Banner a complete wuss, but keeping him cautious. You could see how he could actually get a girlfriend, and that he was heroic underneath his nerdiness. I want the same kind of treatment for Pym. Insecure in that he feels his research efforts just don't match up to the efforts of the guys in the field in terms of bettering the world like he set out to do. But when it comes down to it and he gets out there after getting his powers either through design or accident (see "Roll of the Pyms thread" for that), it takes him a while to realise he has heroism in him, and potential as a warrior, but eventually it shines through. Possibly through his finally hearing Jan when she tells him she believes in him, and sound words from Cap in a moment of Giant Man being down but not quite out.
Tony Stark above has it right - an ensemble can work well if they make the Big Three Spock and Kirk; and make Hank, Jan, Clint and Natasha Bones, Sulo, Scott, and Uhura.
7 Core characters can absolutely work. With Fury in as situation demands (no need for him to be in battle, or running ops for a battalion of marines, or to give him some private scenes etc)