An extension to Seaford, Aldinga and even Victor Harbor is only to be desired- tourism and commuters can only benefit. An alternative route to Willunga would also not go astray, but would either have to transfer into Noarlunga line trains, or the route from Noarlunga to Adelaide would have to become actually independent from the road system: the volume of trains would otherwise mean, for example Cross Rd, would be closed most of the time. (I have long thought Cross Road should pass under the rail line at South Rd- then you have three significant arterials moving independent of each other.)
You may point out the inconsistency of that compared to my position on the Anzac Hwy/South Rd intersection, but the two are fundamentally different: the Cross Road underpass would allow an increase in **rail** traffic, whereas the Anzac Hwy underpass allows, presupposes, encourages an increase in **road** traffic.
In any case, it is to be hoped that the Federal Govt. sees Seaford of worthy of money, because in this climate where even AAMI is neglected, I have diminishing hopes for a rail extension.