I doubt the 748F is anything but a Cat D aircraft and if this is the case, as it has already been mentioned, it would mean for an instrument approach onto runway 12 they would have to conduct the RNAV-Y procedure (with compliance from Oakey) which makes a lot of this discussion about the RNAV-Z procedure moot.
NowThatsFunny:
You're trying to tell people who actually fly this approach what they should be seeing based on a "not to scale" chart.
I acknowledge that you may have first hand experience of conducting these approaches, however I have reservations about your statement. Since when are approach charts (not SIDs and STARs) "not to scale"? If you use Jepps I suggest you look at the left side of the chart, if you use DAPs I suggest you look slightly right of the MSA diagram (where it states "Scale 1:500,000").
Given that both the RNAV-Z and RNAV-Y share the same MAPt (BWWNM) and that the RNAV-Y has an inbound course of 122° which matches the runway track of 122°, unless the approach course is offset from the centreline (which I doubt, but I don't have first hand experience at YBWW) resulting in the approach being parallel to it rather than on it, I can't see some of these manoeuvres described previously being required. Given that BWWNM is 0.8nm from the threshold (as stated on the chart) I'd say these manoeuvres are being conducted due people interpreting the visual cues in a way that makes them think that they won't intercept the centreline prior to the threshold rather than a fault with the approach design (however these approaches are designed by humans therefore it is possible that there could be errors).
As for the comments about the PAPI, I could easily believe that as it wouldn't be the first place and probably won't be the last to experience that issue.