Seven frequencies? So, I think this means
VB wants to start with a daily service between SYD and LAX. They can use handmedown A340-300s or 747-400s from Virgin Atlantic, or perhaps 777-300ERs or 777-200LRs white tails (from Emirates?).
VB might feel they owe a bit to their home town - BNE - and if they want to serve MEL, that would be better if it could be a non stop, which would affect choice of fleet.
If they fly to LAX they will be using the US West Coast's least popular gateway (you use that airport because you have to,) SFO would be nicer except on foggy days
So, if
VB gets seven weekly frequencies, and that is the limit, they may find themselves reaching the limit very quickly.
Other point - United is not a minor competitor, and should not be written off. Every Southern Summer recently, UAL has added three weekly flights on SYDLAX and SYDSFO, making 10 services per week on each route. UAL has recently expanded its flights on the North Pacific - if UAL thought it could make money from running a second daily SYDLAX service year round it would find the planes somewhere.
IF UAL gets its act together it will be very strong competition for both Qantas and Virgin Blue