IMHO, if the goal of the tournament is simply to hold it, then it can be done on the original game. However, if the goal is to attract new players to the TE mod, then it should be played on that mod. Participating in the tournament might motivate many to learn the mod. A thread could be created where newcomers can ask questions about the mod, as there are people who can answer them. If the tournament is successful, similar ones could be held from time to time to attract new players.