This is a very innovative project and I hope you pursue it regardless of yc funding or not. There's lots of Windows apps that would be useful to run in a browser :)
I definitely wouldn't hire someone who played for 40 hours a week, but if it's more reasonable, like 10-15, it essentially becomes a replacement for stuff like watching tv or movies.
The problem is that games like WOW are designed to be addictive, especially at the endgame levels. My college room mate ended up playing for more than 2000 hours before he quit, and it's not been great for him - he's been jobless for two years since graduation.