As noted on my thread, I
would suggest you take the BS/ME route if you are definite you want to be an engineer. This is because you'll have more tech electives and you can always tack on an MBA after a couple of years of experience if you want to move into the finance / management arena.
On the other hand, some firms really enjoy Comm / Eng graduates because they have both the financial and tech knowledge (albeit a little lower tech knowledge) and will move up the financial rankings faster (or so I have heard). In the end, you'll have to toss up between the course structures.
BSc (Soft. Sys.)
BComm (Major + Soft. Sys. minor)
If you do B.Comm, you're missing:
ESD1 (no problem here for you, it's geared towards ChemEng),
ESD2 (kind of a problem because it serves as an intro to MATLAB but not a hassle because you'll be taking first year Informatics / Comp Sci classes) - Informatics 1 and 2 is now called Intro to Computing and Intro to Algorithms.
Linear Algebra / Discrete Structures - Kind of necessary towards a Comp Sci major, not sure how important it is for a Software Eng major. Discrete mathematics is the mathematics of computation, so it's kind of a worry that you won't be taking these. Discrete Maths is also a pre-req for some Comp Sci units in the CSSE faculty, so you'll have to make it up somewhere I think.
And you'll have to take Engineering Communications - a necessary management class / ethics class for engineering because you didn't take ESD1 (the ethics portion in ESD1 is run over 2.5 weeks instead of an entire class like Eng Comm).
However, by missing these, you'll be taking a major in Finance or something. If you think it is worth it, I would suggest you take BComm / ME, however, if you are certain you want to do technical engineering (less focus on project management straight away), I would suggest a BS / ME pathway due to the large amount of tech electives youll take in comparison to the alternative pathway.
Note: I'm not a Software Eng major and this is really the first time I've looked at the course. Since you'll be starting in 2013, you'll be undertaking a "Computing and Software Systems Major" which allows you to branch of to do a Master of Science - Comp Sci or a Software Eng Masters.
https://handbook.unimelb.edu.au/view/2013/!B-SCI-MAJ%2B1037?output=PDF
Page is down ATM, but it should be up later.
If you have any more questions, feel free to ask.