Custom language that displays content from two languages
The whole idea of linking language with country falls apart when you consider countries like Canada. You could separate language and applicable country since they're not really the same thing. In your example:

Australian Website


Home (Lang: English - Country: UK, US, Canada, Australia)
About (Lang: English - Country: UK, US, Canada, Australia)
Products (Lang: English - Country: UK, US, Canada, Australia)


Product One (Lang: English - Country: UK, US, Canada, Australia)
Product Two (Lang: English - Country: UK, US, Canada, Australia)
Product Three (Lang: English - Country: Australia)
Product Four (Lang: English - Country: Australia)

Resources (Lang: English - Country: UK, US, Canada, Australia)
Contact (Lang: English - Country: UK, US, Canada, Australia)