For qldrail to come to TSW4 would make lots of the people happy and show other people new and unique trains and routes. Now QLDrail does have many lines but even 1 line for a DLC like the Shorncliffe/Cleveland line. This would be really fun as the trains are very different but amazing as well as having a fun route to explore Brisbane with underground stations like central. The Shorncliffe line would be enjoyable as it doesn't have constant stops or long stops but a mix. For a DLC with 2 trains and 1 route that is truely immersive would make many Aussies happy and other people around the world as we only get European maps.
I support all Australian suggestions, but you must give more details in your post. Have a look at the formats of the most viewed suggestions to get an idea of what I mean. I reckon the Airport/Gold Coast line would be the best from southeast Queensland, for the higher speeds yet still urban feel.