I'd have to agree with Rick. Not to be too down on your idea, but it presumes that people have to live a fair distance from where they work. I would prefer just to live close and bike the whole way.

However, if a park-and-bike were being built, I would suggest that if have dedicated bike paths to the center city, with no (or at least a minimum) of road intersections. Have lots of bike lockers for people who don't want to have to load their bike on and off their car every day. Allow overnight parking (perhaps with a parking pass or something) for people who drive in, bike home, next day bike in, drive home.