I think Delly would be behind Bryce Cotton, Caspar Ware and Melo Trimble for best guard in the league, but not by a lot. He would be comfortably the best Australian guard and arguably would run a team better, but those guys would put 20 a game out and he'd be like 10-12 ppg, 6 assists, and some good D. As said before, Damien Martin with some offense.
Thon Maker would be an upgraded Majok Deng. Probably a starter. But he has too many holes in his game to be a MVP candidate. Would probably rise to that level with time though. Would make some great highlights and be vuery good though.
Exum, with his physical skills, would probably average over 20 a game. I don't see anyone stopping his first step. He would be like Joe Ingles first year in the competition and perhaps better.