I'm pretty sure in a Bachelor of Science in Melb, you can practically do anything a BioMed student can (except 1 unit I think). There is practically no difference in the degree other than the name if you're leaning towards the medical/pharma kind of things.
For example, I have a sister who just graduated yesterday with a B.Sc. 3 years ago, she got a ENTER way above the clearly-in score for BioMed @ Melb, but chose to do science due to wanting to keep her options open. 1 year later, she decided to major in pharmacology and took the same subjects as what the BioMed students are taking (Together with the BioMed ppl).
What I'm trying to say is, put B.sci @ melb as your 2nd pred, and keep B.bioMed @ melb as your 1st pref. No harm hoping for a miracle, but personally B.sci @ melb is a smarter choice to me than a B.bioMed @ melb. The only difference is in the name, which wouldn't impact much on your job prospects especially if you choose to further your studies after the Bachelors Degree, while you get to keep your options open.