Howdy Mirakon. To study BA/MBBS (or BA(hons)/MBBS) at UNSW you simply need to make it into the MBBS program and, later, to notify the faculty of your interest in the combined BA program.
Despite what some people tell you, in practice you want 99+ for entry into UNSW medicine. The median UAI/ATAR for entry is consistently greater than 99.6 with the mean sitting only slightly lower (say 99.4?). Of course, you need to combine this with a moderately strong UMAT score. I haven't looked into the changes made to the UMAT scoring system, but intuitively by looking at this table, I would predict that a UMAT of ~ 60+ would suffice with an ATAR in the mid-high 99s. You also need to do well in the interview
- i.e. you need to have some social skills
In any case, from what I can see of your mind through the interweb I'm sure that you stand a strong chance of getting in if you make it your goal. Good luck