I think far too much is being made of the Gold Coast / Brisbane, 'co-host' issue.
Putting aside the notion of holding some team sports events in other parts of the state (which personally I think is a fine idea? And comparable, as Puppy said, to soccer in the Olympic Games), this is no more a co-host scenario than any other in the history of the Commonwealth Games.
The Gold Coast and Brisbane are regions within the single greater metropolitan area known statistically as '(Greater) Brisbane', and they are sufficiently close that both will be utilised in what is still a perfectly palatable plan… The majority of the venues are within 20-30 minutes of the village with three or four outliers within an hour.
Calling this a co-host scenario is like calling Melbourne a co-host scenario because it actually utilised the Local Councils of Moonee Valley, Port Phillip, Maribyrnong etc. Or every games in the history of the thing co-host scenarios for the same reason.
(And in reality, local council jurisdictions in Queensland are as big as you will find, and if there is a single Local Government Area anywhere capable of holding a Commonwealth Games entirely within the confines of its own perimeter then it would surely be Brisbane. Failing that… the Gold Coast.)