Why not attached to a grain service?
Freight is freight.
Grain like coal runs in block trains. This tends to be a world wide approach even in developing countries so I would hesitate to say there is a better way. Additionally the western line trains are so short by modern standards there isn't much option to just add it on to the end.
By and large, mixed services are a thing of the past everywhere. Again there are very good and numerous reasons for this and how many operators does it take to make this valid? The Westie lost its mixed status with QT stopped subsidising freight by rail, nothing to do vertical anything, privatisation etc etc
However as we all have noticed the Westie is 2 x week and short and maybe perhaps there is an opportunity, but would having 1000t of freight wagons with their sloppy couplers on the train make it less comfortable for the passengers. The down side of course once you get to BRisbane what do you do? You cannot run this train to Roma Street!
I would suggest if the meat wagons can store the meat, it would need to run dedicated trains to port direct (lowest cost) and/or once the tunnel work is done and containers are again rolling, its a shunt from Toowoomba to collect the wagons and run a full length block container train down the range for frequently with others products.