I guess if everyone was to register their event as a NOTAM then a particular aircraft that carries advertising would know to avoid the area.
They are pretty specific with hot-air balloons being exempt because they finish flying generally before 9am so it sounds pretty serious and airliners is going a bit far!
If they wanted to get picky it would make things hard. eg. Pip Boorman flies his Edge painted up with Castrol markings into Essendon via Flemington and gets 400 penalty units for overflying the Flemington races! Ouch!