iv seen perth zoo and armadale reptile park keep multiple species together perth zoo has an indoor pit with a clump of upright branches on ither side and a rock pile in the middle, theres 2 frillys that stay in the branch piles, some beardies which stay on branches or rock piles and heaps of shinglebacks and some western blueys, however obviously there is a heat lamp suspended over each branch pile and the rock pile as well as one just on the sand so there is ample basking spots which will reduce the reason to fight over basking area's, your enclosure could work with the frilly and the bluey but you would need a ground basking spot for the bluey and a basking spot on upright branch for the frilly