Welcome to MSO
I will respond under the assumption that you're planning to apply for graduate entry medicine through the GEMSAS system. Please correct me if not.
From these options:
1. Your GPA for graduate entry medicine is going to be calculated using units from your nursing degree if you do this, so I wager that unless the grades are not as bad as you say they are, this won't fix your GPA issue entirely. All GEMSAS schools will calculate GPA using 3 FTE years of study, so in your case your final year GPA would come from your paramedicine degree, the final-1 year GPA would come from a combination of units from your paramedicine and nursing degree (depending on how much you get credited) and the final-2 year GPA would come from units from the nursing degree. Different GEMSAS schools calculate GPA differently (most weight the final study year triple, the final -1 year double and the final -2 year x 1 but some will weight all three years equally; this is an unweighted GPA). I'd refer to the GEMSAS guide for more details about how each specific university calculates GPA:
http://gemsas.edu.au/wp-content/uploads/2018/03/2019-Medicine-GEMSAS-Admissions-Guide-v1.4.pdf
2. The only GEMSAS universities that use graduate diplomas in the GPA calculations are UNDS and UNDF (and the other two years are still going to come from the nursing degree) so this isn't going to improve the GPA that much.
3. Only a few universities (I believe Griffith and UWA are two) consider coursework masters degrees for the purposes of graduate entry medicine. If these are applicable to you then it may be a way to go, but limiting yourself to only a few schools is risky unless you actually want to do the masters program on its own merits.
Your alternative options:
- I am not sure if you have sat GAMSAT before. If you achieve highly on GAMSAT, you can apply to USyd and/or UQ (which use a GPA of 5.0 as a hurdle requirement - I am unsure if you currently meet this) which base interview invites solely on GAMSAT score once you've met the GPA hurdle.
- Sit UCAT and apply as a non-standard applicant to the undergraduate schools; JMP and WSU both use GPA solely as a hurdle requirement but as above, I don't know whether you will meet either of these.
- Complete a whole new undergraduate degree which consists of at least 3FTE years of study (i.e. one that doesn't rely on credits from your nursing degree). Ideally you'd do a degree that you actually want to use should you not gain entry into undergraduate/graduate entry medicine (this is the most likely outcome for anyone pursuing medicine entry). If you were to do this, I'd recommend you do it at Flinders if possible to gain entry into their Flinders grads subquota, where the entry requirements are lower than the GEMSAS schools (albeit still competitive).
If you give an indication of what your GPA for each year of your nursing degree was (keeping in mind your GEMSAS GPA will possibly be higher) and whether you are a rural applicant, this will help us give you more informed advice.