I don't know too much about Open Universities but it seems you would be effectively giving up the uni lifestyle of meeting people, partying etc. and studying purely online. And if you didn't get the grades to be able to transfer mid-semester into Latrobe, does that mean you would be stuck studying your degree online? Or are you guarenteed entry into a university in Victoria?
I think you would be better going to Deakin University or RMIT and studying a commerce degree there. Then after six months you could attempt to transfer into Latrobe. You would most likely still get credit points for the subjects that you completed in the first semester and you would have experienced the uni lifestyle.
I'm studying a commerce/law degree at Deakin and I have found commerce to be pretty interesting so far with quite good lecturers and a really friendly atmosphere. You should defintely consider it as an alternative option if you don't get into Latrobe.
Hope this helps