Guys, if u interested in such tennis quizzes, I can give an idea (realized by me in the russian tennis forum) for team's ONLINE battles on basis of Russian TV show "BRAIN-ring". There are 8 teams (maybe national teams) for 3-4 players. so you will have 4 Quaterfinals, SFs and Final. Every match has two sets (till 6 points) and super-tie if it need (1 question). Both Teams are online when match starts. Manager gives question. Teams have 3 (5) minutes maximum for each question. Team get 1 point after correct answer of one of members. If answer incorrect, another team should give answer. if answer of second team is incorrect also, manager should ask another question (another game begins)but this question will cost 2 points. If one of teams answers this "2-points" question, next question will cost 1 point as usually. First set finish after 6 points of one of teams. Team wins after 2 sets. So you need about 15-20 not difficult questions for every match, 100-120 questions for all tournament, several authors of questions and 2-3 managers of this event. So it is funny irregular event for off-season
I don't think time-limited questions will work well in an international forum format.