In a strange way, the local Kingsford Smith branch of the ALP are correct on the subject of preselecting Peter Garrett, but for very different reasons than they probably think. Peter Garrett would do more harm than good as a member of a Latham government, and would be a real distraction on the front bench of a Labor Opposition. There is no reason to think that Garrett's role would be dramatically different from that of Cheryl Kernot.
Both Kernot and Garrett are individualists at heart, and are not used to playing a team game. For Kernot, being a minor Labor luminary rather than the star of the show was a blow to the ego, and Garrett is likely to face the same fate. An honest appraisal of his political potential shows that Garrett would need to build support and experience over time, and grow gradually into the role, which would be supremely difficult given his profile.
Garrett as a Green would work - he'd share a high profile with St Bob and be a senior part of a small group. As an Labor member, he'll be a small part of a big team, and end caught up in internal conflict and finish with a bruised ego. Not a good look.