From my POV the above does not appear to consider some of the key factors revolving around logistics. Namely the size/volume, and weights to be lifted, and over what distance. IIRC one of the things which had been happening, and part of the reason why the RAAF and before that the US Army was looking at the C-27J Spartan, is that very often a C-130 would be used for an airlift whilst being half empty, because of the distances the load needed to be airlifted. Now something like an A400M can certainly lift a larger sized piece of kit, as well as a heavier one, over a longer distance. However, the RAAF already has the C-17 which can lift more than an A400M. Adding A400M into the mix seems to be an expensive option, unless the ADF has an even greater need to carry outsized loads strategic distances, which the C-17 fleet cannot meet.
Unfortunately with the C-27 no longer in USAF service as an airlifter continued support and development for the platform has largely ceased and IIRC the RAAF was finding it difficult if not actually no longer viable as a battlefield airlifter. The Beech 300-series aircraft are decent as liaison aircraft as well as variants for EW and ISR roles, but due to their small size and layout, are really inappropriate for airlift. IIRC their max personnel lift is 11, or up to ~3,000kg of cargo but that cargo cannot be palletized due to cabin and door dimensions. The CH-47 medium lift helicopter is certainly capable, but has range and speed limitations. This ends up leaving the C-130 as being the go to aircraft to get personnel and kit to either where they need to go, or to logistics hubs where then other transportation options can be used.