Nothing wrong with multiple entries imo. More questions = less chance of repeated question. It just becomes increasingly harder to find unique trivia questions if people spam several dozen questions at once.
If you meant 1 entry for the prize, then yea, 1 per.. but GM's are typically already checking for duplicate entries anyways. So if they see multiple entries from someone they picked to win, they will void it and pick again.
The real question though is how hard is it to change the trivia question pool. If GM's don't have access to the database, then it will have to go to the devs which may take some time.