Agreed,
I see Dark Green Merc Vito vans up and down Mt Lindsay Hwy/Beaudesert Rd without fail at least once a week, and sure enough there is a tiny sign about 400x500mm tucked away in front of the van where you can only see it if you're looking for it, or driving in the opposite direction, and to top it off, you can barely see the "police" lettering on the sides fo the van due to the dark colour.
Furthermore, i saw a nice officer who had parked down a side street, maybe 50m down, and walked up to the intersection, standing behind a sign with his trusty camera out.
Essentially, if they want to slow people down, hiding and using unmarked vehicles isn't going to change anything since no one knows they're there.
It's been said 100 times, their goal is clearly not safety, but revenue raising.