would you suggest doing Physics fast-tracked? 
Best place to ask is probably int he Physics board! But it really depends on how you are going with the physics in year 9/10 science, and whether or not you do 1/2 in year 10. I think you really need 1/2 to go onto 3/4, but others may disagree.
I'm going to assume one of two situations here:
You're going into year 10 and will be doing the 1/2, or you're going onto Year 11 and will be doing the 3/4.
If you're going onto Year 11:
I would suggest doing the 1/2. It's possible to do physics 3/4 without 1/2, but it'd be a lot easier with the 1/2 background knowledge. As you've been given the option of doing a 1/2 (by doing 1/2 in year 11 and 3/4 in year 12), I wouldn't give that opportunity up.
One of the advantages behind accelerating is that you get a really solid score before you enter Year 12 - easing up your stress slightly. You can't really judge if you'd like Physics 3/4 without doing 1/2. Physics in year 9/10 is pretty different than 1/2 and 3/4. How much you enjoy physics is also really dependent on the teacher, and the majority of physics teachers seem to be not that great. By doing the 1/2 you can learn how you'll have to approach learning physics at your school - rather than being thrown in the deep end by going straight into 3/4.
If you plan on skipping the 1/2 of a subject, I don't think physics is a good subject to go straight onto the 3/4, when you could select a better subject that you can guarantee you'll enjoy and excel in.
If you're going into Year 10:
If you do the 1/2, then Physics is probably one of the best subjects you could choose to do fast tracked (if you're a sciencey type student). I'm really glad I've chosen to physics early.
Others will disagree, but I wouldn't like to do something like maths (except for maybe further) or an English subject accelerated One year less of learning would be a serious disadvantage for those subjects (not to say that you could still do extremely well with the correct aptitude). Physics is a fairly maths-light subject and it'd mean one less midyear in first semester of Year 12.
I don't know where you plan on going after Year 12, but it's not an absolutely necessary subject - if you don't do that well, you're not going to lose that many course choices - most will require either chemistry or physics or biology (if you do one of those other subjects you'd have that to fall back on).
If you decide you don't like Physics in Unit 1 and 2, then you can switch into a different 3/4 when you get to Year 11.
To summarise, do Physics 1/2. It'll help you a lot. If you're going to skip a 1/2, there's probably a better subject choice out there.