This is a really good post. I just want to add some context to his D.
From my perspective Bell improved a lot defensively from Freshman to Sophomore year.
Because we had to play the year mostly without a real power forward, Bell guarded power forwards a lot, and he's not built to do that. When he was guarding smaller guys he did a pretty okay job.
I found it interesting that when Brown played center and got pushed around, most fans noticed he was out of position and wanted to get a center on the team to help, but when Bell was playing power forward and got pushed around, nobody complained about him being out of position, they just complained about him being a terrible defender.
I think Bell will be stronger next year and a better defender, but I also think having Freeman and Brown at power forward, allowing Bell to guard wings as he should be doing will make a big difference. I predict there won't be any defensive problems with Bell next year.