I almost suggested Italian (or specifically a pasta specialty). There are quite a few options that can be passable from a Bain-Marie out back in the kitchen. Lasagna of course can easily be done in bulk and served up.
For Adelaid Le
German Hahndorf & Barossa
Seafood. Port Lincoln tuna or fish or coffin bay oysters
Champagne
Vietnamese
Italian makes a lot of sense for Adelaide. The problem I see is that I have little faith it will be implemented well. Put up a paltry effort and every Italian mama in Adelaide will be assaulting the lounge staff with wooden spoons, and it will be deserved.
Lasagne sounds great until you realise everyone will take the edge pieces first (or pass up the tray until a new one comes out with edge pieces), plus I have little faith in people to actually dish up a block of lasagne (let alone a scoop) neatly. It's gonna look like a dog's breakfast (or what it ate, but thrown up) very quickly. Taking a step back, if the lounge doesn't bother to make a good lasagne al forno in house and just get a mass catered one... I'm sure we've had enough of those, and they are horrid (the sugo is tasteless, the cheese is cheap and there's hardly any meat).
Pasta dishes sound great except that the longer pasta sits in a hot tray, the worse it gets because the pasta overcooks quickly. Refreshing it to be of quality at all times would waste a lot of pasta. You could do pasta to order to overcome these difficulties, and I think that would be nice, e.g. one penne arrabiata and another is pesto handkerchiefs
(cue everyone saying you just picked two of the worst ideas as examples).
Pizza is an option, but that copies Perth.
Some quality antipasti, served with charred Italian bread, would be a winner, but it has to be
good quality stuff, i.e. not just Don salami which you get at the supermarket.
German food... I see plenty of pork and potatoes in that. Sorry, Germans.
Tuna or fish might be offered as plates of the day. I wouldn't go down the sushi path as that's likely to be mass made and horrible. Maybe sashimi sliced to order during peak times (I'd say that'd go extremely fast, particularly if you don't limit how much people are allowed to take at a time). Oysters - hell no (not because they are disgusting, but because without live supervision and proper handling of fresh oysters, you're inviting a health / food poisoning suit).