What you're saying simply isn't true. Things were a lot easier 4 years ago, it was easy for you, but simply it isn't like this anymore.
If you read the Partner migration booklet (which is a MUST if you want to apply for a partner visa), you'll see that on the page 35 it says:
De facto partners (not married but in a de facto relationship)
To apply for a Partner visa as a de facto partner, you and your partner must show that you have been in a de facto relationship for the entire 12 months immediately prior to lodging your application. For details on the 12-month requirement, see page 18.
To be eligible for a Partner visa as a de facto partner, you must:
• be sponsored by an eligible person (usually by your partner) (see 'Sponsorship eligibility' on page 14);
• not be related by family;
• together with your de facto partner, be aged at least 18 years at the time your application is made;
• show that you and your partner have a mutual commitment to a shared life to the exclusion of all others;
• show that you have a genuine and continuing relationship with your partner (see page 39);
• show that you and your partner have been in a de facto relationship for the entire 12 months immediately prior to lodging your application;
• show that you and your partner are living together or, if not, that any separation is only temporary; and
• meet health and character requirements (see pages 19-21).
In assessing a claimed de facto relationship, the department looks at evidence of things such as living together full-time, sharing important financial and social commitments, and setting up a household separately from other people (for acceptable types of evidence, see page 39).
You need to have all the evidence prior to applying for a de facto visa, the evidence you provide later doesn't count.
Have a look at this case, it's a great example how important the evidence is for a de facto visa.
1007797 [2012] MRTA 1702 (18 June 2012)
If you come over on an ETA visa, get married first and then apply for a partner visa based on marriage, you still have to provide evidence (it's all in the booklet). You could get married straight away (when you come to Australia), then create good evidence in the following three months and apply shortly before your ETA expires (towards the end of your three months). In this case it'd be good to provide the evidence you already have (skype logs, emails, phone stats, etc.) to prove you didn't just started your relationship.
Bridging visa is rarely given straight away. That used to happen when people applied in person and they only had a few days left on their original visa. If you check this forum, you'll see you can't apply in person anymore; the applications need to be sent by post. Those applicants who insisted on applying in person and post on this forum wrote how disappointed they were, thinking somebody was going to check their application or talk to them when they applied; this doesn't happen anymore.
Bridging visa kicks in automatically when your original visa expires, in your case in three months, in case of longer tourist visas in six months or even a year (depends on the visa). Since November 24 2012, bridging visa A for partner applicants comes without any work or study restrictions. But your original visa needs to expire first, in your case that would happen after three months.
Regarding PMV, if you check the booklet you'll see you hardly need evidence for that type of visa.
I'm not a registered migration agent, but just somebody who went through this partner visa process myself. I suggest you check this forum thoroughly, there are many posts on the same subject weekly, do the research and then decide. You're lucky cause you have many choices, you can decide to apply for a PMV or an onshore partner visa (based on marriage). In case of applying for a partner visa, you can't apply without getting married first, as you don't have enough evidence for a de facto visa (check the upper MRT case).
That's what I did when I got here 4 years ago. You both go to immigration, pay the fees and done. You get a bridging visa straight away. During the 2 years process you might be asked to take some more documents to your case, or coming for a interview at the DIAC. But, if this relationship between you and the Aussie girl is true , there us nothing to be afraid. No dramas mate and easy as.
Applying for a partner visa is a 2-stage process and approximately 2 years after you first made your partner visa application, you will be assessed for the grant of the permanent partner visa (subclasses 100 or 801). Yes, you will be invited to present more evidence about your relationship when time comes for the second step. But, this has nothing to do with your original application; as I said, if you apply for a de facto, you'll be assessed based on the evidence you attached; if you apply for a partner visa based on marriage, you'll be assessed based on the evidence you provided and they might want to ask you for some more evidence before granting your temporary partner visa.
This is a photo of our onshore partner visa application, and we were married and had evidence in all four categories.
Good luck.