Fiji is a given + maybe NOU & some pacific islands
I don't think Fiji is a 'given' at all. Particularly as JB has said he wants business class on the Fiji flights.
As for NOU, the reason Virgin don't fly there is the high landing charges (PB looked at it years ago & the landing charges made it unviable). And if costs prevent Virgin flying there, I don't think that Tiger will be going there any time soon.
As for Tonga, Samoa & Rarotonga, they might be able to offer a viable service to those destinations.