I think the Virgin domestic system is the best of both worlds, they use a mixed crew of AMEs and LAMEs. They both do the turnarounds, if the arriving aircraft for an AME comes in with a defect then he swaps with a LAME.
The LAME fixes the aircraft and departs it, the AME departs the LAMEs original a/c.
This way the aircraft gets a look over by a set of trained eyes, rather than a non-interested bagchucker. And the company gets it savings by having more AMEs doing turnarounds.
Great in theory, but when you have a management as uninterested as the bag chuckers, the cheapest denomination always wins out. i.e. bag chucker who doesn't need trained eyes, so he/she won't find anything. Commonsense isn't so common in QANTAS management. They're more interested in saving common cents.