In my opinion the key considerations in that scenario would be:
1. Could Longstreet resolve the command dissension in the Army of Tennessee? The AoT was a viper pit, of those wanting Bragg removed, Johnston was likely the most favored successor. Davis had also mentioned to Polk that part of the reason he sustained Bragg at this time is because he lacked confidence in Johnston, Beauregard and Longstreet. If being put in place after Chickamauga Longstreet would have been faced with potential Corps commanders like Hardee, Polk, D.H. Hill and Breckinridge. Longstreet and Hill were not best of friends, but they agreed Bragg needed to go. Longstreet was senior to the other Lieutenant Generals, Hardee and Polk, so perhaps they would have agreed to stay on. Organizing this group into a cohesive striking force though would have been a challenge for anyone up to and including R.E. Lee. Longstreet did though show some difficulty in the question of command cohesion during the Knoxville campaign, falling out with several key subordinates including McLaws, Roberston and Law following the battle.
2. Could Longstreet plan and implement and offensive operation at Chattanooga, or subsequently in the Dalton area? Longstreet's limited operations acting independently like Knoxville or the Suffolk campaign are not tremendously inspiring. Though he did demonstrate significant offensive capabilities as a subordinate commander at Chickamauga, the second day of the Wilderness and Second Manassas. But taking that next step to be the overall commander can be a big leap as demonstrated by what happened to Hooker, Burnside, Pope and others. With Grant, Sherman and Federal reinforcements pouring into Chattanooga the challenge was becoming more significant by the day.
Overall it is an interesting consideration, perhaps he could have pulled it all together and been more successful than Johnston, though like all of these what-ifs it is so difficult to make a real determination.
In my opinion the key considerations in that scenario would be:
1. Could Longstreet resolve the command dissension in the Army of Tennessee? The AoT was a viper pit, of those wanting Bragg removed, Johnston was likely the most favored successor. Davis had also mentioned to Polk that part of the reason he sustained Bragg at this time is because he lacked confidence in Johnston, Beauregard and Longstreet. If being put in place after Chickamauga Longstreet would have been faced with potential Corps commanders like Hardee, Polk, D.H. Hill and Breckinridge. Longstreet and Hill were not best of friends, but they agreed Bragg needed to go. Longstreet was senior to the other Lieutenant Generals, Hardee and Polk, so perhaps they would have agreed to stay on. Organizing this group into a cohesive striking force though would have been a challenge for anyone up to and including R.E. Lee. Longstreet did though show some difficulty in the question of command cohesion during the Knoxville campaign, falling out with several key subordinates including McLaws, Roberston and Law following the battle.
2. Could Longstreet plan and implement and offensive operation at Chattanooga, or subsequently in the Dalton area? Longstreet's limited operations acting independently like Knoxville or the Suffolk campaign are not tremendously inspiring. Though he did demonstrate significant offensive capabilities as a subordinate commander at Chickamauga, the second day of the Wilderness and Second Manassas. But taking that next step to be the overall commander can be a big leap as demonstrated by what happened to Hooker, Burnside, Pope and others. With Grant, Sherman and Federal reinforcements pouring into Chattanooga the challenge was becoming more significant by the day.
Overall it is an interesting consideration, perhaps he could have pulled it all together and been more successful than Johnston, though like all of these what-ifs it is so difficult to make a real determination.