Sprinklers are not essential but without sprinklers, according to NCC 2022 clause S5C20 (2), the carpark in the lowest storey and the floor between it and the Class 2 part above would have to be of concrete or masonry. So the lowest storey is virtually a concrete/masonry box with the timber-framed Class 2 occupancies on top.

We assume the existing pine mouldings are too easily dented or damaged and a harder timber species is needed. Common timbers have been rated for hardness according to a standard indentation test. Pine is rated 3.3 on the hardness scale, whereas blackbutt is 8.9 and spotted gum 10.1. Not all timber merchants can supply mouldings in Australian hardwood species but moulding specialists such as Rallis Timbers should be able to help, website here http://www.rallistimber.com.au/milling-mouldings.html. 

Unfortunately we are not aware of anyone stocking or producing the textured hardboard shown in your photo. Hardboard is not MDF, it's a sheet product known in earlier times as Masonite. It is now produced in a Standard Grade and a "tempered" version, but not with an overlay as far as we are aware, more info via this link https://plywoodaustralia.com.au/hardboard/. Hardboard is also produced as an external cladding material under the brand-name Weathertex.

American red oak was not included in Warringtonfire's tests on wall and ceiling linings, only American white oak as per our Regulatory Information Report RIR 45980.10. However, red oak has been confirmed as a Group 3 material in a separate report which we will send direct to your email. 

Timber is relatively unaffected in a salt-laden environment, hence the number of structures in coastal areas which are traditionally made from timber (jetties, boardwalks, steps down to the beach, etc.) One type of degradation that has been observed in coastal areas is "defibration", explained in a US Forest Products data sheet that can be accessed via this link https://www.fpl.fs.usda.gov/documnts/techline/Techline_06-2011-001.pdf.