Ironically the original requirement that led to the MRH buy was an additional troop lift capability, primarily to operate from our existing and proposed amphibious ships, Bill, Ben and Tobruk initially then the LHDs, not a Blackhawk replacement per say. I am not sure but I believe this was part of the white paper decision to acquire LHDs, making it very surprising we didn't select a fully sorted / marinised type in the first place.
This additional capability was, I believe, to be in the form of an additional squadron, with no specific type being specified, just "x" number of troops ship to shore in "y" lifts over "z" range, load, sea state etc. Lima Blackhawks and Merlins were offered up with NH90 TTH (tactical transport helicopter) being successful and twelve examples ordered. Then as part of the desire to reduce the number of types in service, a second larger batch was ordered, if memory serves me, without a formal competition to determine whether upgrading the Blackhawks, new Lima or Mike Blackhawks (or another type) was the best way forward, despite the Army's clear preference for Blackhawks. Then the Seaking replacement was brought forward and Aerospace Australia got an automatic, non competed order for an additional six airframes.
The assumption was, even though a multitude of schedule, certification, durability, performance, quality, design and development issues were becoming apparent, that the NH (naval helicopter) variant would be selected to replace the Seahawk and Super Sea Sprite shipboard helicopters, if only for the sake of commonality. Fortunately the government of the day listened to the capability people and operators, ordering Romeo instead, leading to a much smoother acquisition and introduction into service.
In hindsight, the thing that appears to have gotten the MRH across the line was it was newer and had a larger lifting capacity than the Blackhawk, as well as a lower cost of ownership and being small / versatile enough to be considered as a Blackhawk / Seahawk replacement going forward. As it turned out cost of ownership was grossly understated, project status was greatly over stated and on paper performance has been significantly impaired by the actual, layout, ergonomics and durability of the design.
Hindsight is great and I can see why the NH90 concept was so attractive to government at the time but without the plan to reduce the number of types in service it is clear that either an S-70 derivative or even Merlin for the initial increased troop lift requirement would have been much better going forward. Blackhawks (possibly modified for shipboard operation), Knighthawks (Sierras), or Merlins for the additional lift, refurbished / upgraded and / or new Blackhawks to replace the existing fleet, Merlins or Sierras to replace the Seakings and Romeos or a mix of Romeos and Sierras (or even Merlins) to replace the Seahawks and Sprites. Lower acquisition costs, lower through life costs, greater capability and easier, earlier FOC.