Is it possible to book 2 separate seats/tickets under the same name on the same Virgin flight?

I have an upcoming overseas trip, with a domestic leg from Brisbane to Perth. Because this domestic leg was ticketed as part of the international flight it is a code share, as such I cannot in any way (points or bids) upgrade this flight to business class.

I was wondering whether it’s possible to just book a totally separate ticket on the same flight in business class? I would obviously check my baggage through to my international destination on the code share ticket, and use my new ticket for the seat only.

would VA have any issues with this?

I foresee check in problems here. You would be well advised to contact Virgin customer support.