I'd love to see a 30k rectangular ground built on the site of the gabba. It would fit better on the footprint of the site without hanging over the road and would actually be a useful addition to our stadium setup. Well located for Roar, Reds, NRLW and smaller Dolphins games.
As far as cricket and fumbleball are concerned, I really don't five a f**k to be honest but a better idea than Vic Park (golf club was closed to make it a green space), is doing an oval stadium at the RNA Showgrounds in Bowen Hills which would be serviced by the new Cross River rail. 45k is more than enough though.
Then fill the corners in at Suncorp and / or build a new western stand to bring the capacity up to 65k.
Then after the games you have:
65k major rectangular stadium for Broncos, Dolphins, SOO, Magic Round, Socceroos, Matildas
45k Oval for Cricket and VFL
30k rectangular stadium for Dolphins, WSOO, Wallabies (lol), Reds, Roar and some lower drawing RL internationals.