Shorter races will definitely help with getting an audience who don't like the boring 60-90 seconds in middle section of 2100-2200m trots when nothing happens. Still a fan of more racing though. 9 race cards are better than 7 race cards etc.
Melbourne Cup is once a year. Rest of the year the gallops barely have races over 2000m+. Typical card 90% of races 1600m or less. Also - have a look at the rise of 1200m Everest and decline of Melbourne Cup in recent years.