Well you say RTW, but unless you go SYD-LHR via the Americas then this isn't going to be RTW. If you did do it that way then SYD-JFK-LHR-LED//PEK-SYD would, I think, be a valid OneWorld Explorer (xONE4). Obviously you could add a lot more into the ticket since you would have 20 segments available.

For other suitable fares it might help if you tell us which class you expect to fly in.