If I may add, you can hold trading competition as well. This will engage traders to stay on your exchange. Some users have no funds to participate so you can hold demo trading contests where you can provide them virtual USDT in their demo account. You can check other exchanges that are doing this to have an idea how it is being done. And at the end of the contest, they can get real rewards. It should be done regularly so the interest will always be there.
IMO this idea won't give the result you are trying to say. Since what you are trying to promote is a event within the exchange itself doing so will only make the project promote the event itself not the exchange so what they will be doing is to promote the event as well as the exchange so they will just be spending more in promoting their exchange. Also they need to consider if they have enough players online using their exchange to see if launching that kind of event is even worth it since they might not reach the goal they are trying to do.