This world takes place in a continent with advanced 20th century technology. The one key difference from our reality is that war does not exist in the way we would think of it. Disputes between states are settled in ritual combat, where both sides choose an individual or groups of people to represent them. These groups would battle each other in games similar to the Olympics, which would be devoted to some deity. These games would take place annually, and also be used to resolve conflicts between nations when other alternatives have been exhausted.
This continent is divided up into various nations that worship a monotheistic deity. A religious order devoted to this god is present in some form among the states. All countries annually contribute to this order, and is protected from being interfered with by remaining neutral. These priests administer this faith amd maintain the peace between these countries through these war games.
These events would open up with a ritual human sacrifice conducted by the priests to earn the favor of the god. Games would put the best of the best from respective nations against each other. Games would have different venues. Some would be dangerous sports that would be played between teams in which death may be possible. Others would be more combative, with the purpose being to kill your opponent. Because of these events, outright war among humanity has been avoided for millennia. Those who die in these events would be considered blood sacrifice to the gods, and would be considered heroes for representing their nations.
I would like these events to serve as a suitable replacement for warfare, and have countries be encouraged to support this system. How could I make this work and remain sustainable in the long term?