So much wrong with this.
point 1. Having a 2nd Centrally located Brisbane side makes zero sense.
Dolphins hit the North. The trade off is a game or 2 to keep fans and sponsors in that part happy.
Same would apply if an Ipswich/Western Corridor came in, You will get Brisbane people but also Toowoomba is closer.
That is why you expand. Only looking after central Brisbane is just a dots on the map exercise and makes zero sense
Man Utd and Man City, Lakers and Clippers, Giants and Jets, Yankees and Mets, Celtic and Rangers, etc, etc.
All of them represent effectively or literally the same geographical area of their cities. Most of them share a stadium, the ones that don't are a short distance from each other, walkable in some cases. All of them aim to represent the whole city, and many of their rivalries are founded on a fight over which is a better fit to represent the city's culture and values.
There is a truism in marketing that the more accessible and convenient a product is the more successful it will be, and centrally locating your team in a place that's easy for as many people as possible to get to and appealing to as broad a portion of the population as possible will always be a more successful long term strategy than the alternatives. It just is what it is, and it's a major reason why the AFL's strategy in Melbourne has been significantly more successful than the NRL's in Sydney.