Maybe something similar to
escapeartist.com, specifically for china.
Focus on job placements, finding realestate/accomodations, restaraunts, language classes etc.
Throw on a message board to get people coming back.
There are a growing number of Chinese and foreign companies employing expatriates for short and long term postings.
Not sure if a similar site exists, but if not, you could probably do well by developing.
Good Luck!