I don't think I'd play Bogut and Baynes together very much - makes us too slow. Depending on how healthy Baynes is at the end of this season, I would start him. He's probably a better positional defender now than Bogut and has shown he can shoot the three a bit too. But hopefully with the less demanding NBL schedule, we can expect plenty of good minutes from Bogut too!
I'd probably start one of Motum, Kickert or even DJ at the 4. All guys who can stretch the floor and have enough size to defend opposing 4's. Really depends on who is in the best form at the time, but most likely Motum.
Ingles is probably our best player with Simmons out, so put the ball in his hands and let him create. Mills should also start for his shooting and experience.
Not sure if I'd go for Delly, or put Broekhoff out there for his shooting. It really depends on how well Delly is shooting it at the time. Exum is even a possibility, depending on how much he has progressed by the end of the season. He's not been consistent for Utah, but he has had some good games and his ability to attack the basket is something we otherwise lack from the starters. (Ingles can a bit, but there's less space in the key in the international game for him to get his shot up).
Creek should be in there because he also brings some athleticism we are otherwise lacking on the wings and has some good leadership qualities.
I think Bolden, Maker and even Hodgson are all guys who you want to see compete in camp with guys like Kickert and DJ for the backup big men spots. Maybe Bairstow too, depending on his form by the end of the season.
I agree with the above comment about Barlow. He has really played extremely well this season and would be a handy utility in the 11th or 12th spot.
Goulding is having a poor season so far, so I'd want to see him compete with guys like Gliddon, McCarron and Sobey for the 4th guard spot. Needs to be a guy who can fill it up from deep and make big shots when it matters. Gliddon and McCarron are probably ahead of Sobey right now, but I like the speed Sobey brings, which can be handy against some opponents.
All in all, if Simmons is out, I think there are a lot of spots that should be up for grabs in the Worlds team. I'd probably only lock in Baynes, Bogut, Ingles, Mills, Delly and Broekhoff.