I guess to be realistic at this stage there are probably no standards currently in place. Anyone at this stage could effectively include "Australian", "Australia" in the name of their event.
However I would suggest that only one thing currently will determine whether your event is considered a "National" rather than "State based" or "local" event. That thing is the prizemoney on offer.
The prize payout you attribute to the event will determine if you will attract travelling bowlers. This is the only way you could realistically class the event as a National event.
To attract the travelling bowler you will need to:
1. Have the prizemoney for as many positions as you can guaranteed
2. Have at least a 1 in 3 prize payout
3. Ensure that the final prize positions at least return to the bowler an amount equal to or preferably more than the entry fee.
4. Attempt to have the event accredited by the TBA.
5. Try to get Total bowling, AMF, Goldpin or one of the ball companies on board as a participant in the event.
Unfortunately these days unless people can see a possible return the event won't attract travelling bowlers and without them you just have a local event.