No doubt, those limitations were there regardless. I still think that JB/SU would have helped TB in the draft: 1) by developing him better; 2) by providing a better surrounding cast (IU made the post season but nowhere near the FF 2 seasons ago); and 3) SU players, even arguable second rounders, tend to get a very favorable look from NBS gm.s The last 6 years in a row are no accident.
I don't think it would've been a material difference one way or the other. He stayed a year too long. He leaves after his freshman year he's a first rounder and everyone says he made a great decision. He stayed and it's easy to say it was a bad one. I don't think the outcome in either situation is any different than if he was at SU or IU. As for your numbered points:
1) How would we have developed him better though? The questions aren't around his offense. His stock is hurt by having slow feet in a league where teams target that exact weakness in pick and rolls in space with their guards. Are his feet quicker if he comes to Syracuse?
2) That's very misleading. The F4 was an incredible run for the program and fans, but it's not like we were a consistent top 5-10 team all year long. We were the bubble team. IU was the B1G conference winner who beat UK before losing to UNC in S16 in a game that was similarly competitive to ours. This year both teams were bad but IU was better early on before injuries.
3) I don't like Crean and think he's got a slimy/weasel vibe to him but he's had success with getting guys to the league and is well regarded as well. Wade, Matthews, Zeller, Oladipo, Vonleh, Ferrell had a strong rookie year so I don't think that would've swung the scales much either way.