As I'm reading Castel's Decison in the West, I thought I might make a list of a few PODs for the Atlanta Campaign:
1. At the battle of Chickamauga, John Bell Hood was wounded in the leg, requiring amputation. The surgeon himself doubted Hood's chances of survival, yet he managed to live. If he dies, another commander will be promoted to the vacant corps command. Assuming Cleburne keeps his proposal private, only sending it to Hardee and Johnston, he could receive the command. Snake Creek Gap and Resaca will likely go as OTL, but Cleburne could decide to go ahead with the attack at Cassville that Hood failed to make.
2. Had Johnston properly defended Snake Creek Gap, it's likely Sherman will simply look for another way around the Confederate flank, but could he lose patience and decide to attack their positions on Rocky Face Ridge anyway? If the Union is mauled here, it could allow Johnston to make a counterattack.
3. Johnston initially wanted to organize his army into three corps - one with three divisions under Hardee, and two with two divisions each under Thomas C. Hindman and Mansfield Lovell. Davis didn't approve, probably because of the stigma of New Orleans that Lovell carried. I haven't much support for this, but apparently Davis suggested Lee's artillery chief, William Pendleton, for a corps command, but Johnston declined. It could be interesting to see how some combination of these possibilities work out.
Extra PODs are more than welcome, feel free to suggest any.