I love chess and some interesting PvP games. I never see anyone make a fighting game in online casinos. It will be very fun and I will absolutely join that games. PvP both increase your skill and develop your mind.
PVP game is a hard game to survive, unless he has a great idea on how to develop, manage, and advertise the site. He also have to be very patient person because it will take some months or even years before he can get good traffic on his site. Otherwise, the site will dead as soon as he lose patient after few months.