If you’re super into studying med, how about a BSci/Eng or BSci/Comm at Monash? This gives a kind of compromise. As far as I understand, you’ll need to study certain units to be eligible for postgrad med at Melbourne, which you can only take in science, biomed and some related health courses. (There’s been some other threads around here that discuss the units required, so please look around here and in the University boards for those.) With BComm/Eng, you won’t be able to fulfil the unit requirements for Melbourne postgrad med, as there’s no out-of-faculty elective space.
If you’re doing a double degree involving either science or biomed, I believe this also allows you to compete for Monash’s postgrad med courses too. This should increase your chances of studying med in the future. The other degree will also broaden or provide further direction as to where you can go in terms of career.m, if you’re not fond of a single science degree.
You should still accept your offer though and change your preferences accordingly, otherwise you’ll risk having nothing. You can always transfer or unenrol later on if need be.