It was Bragg’s responsibility to have a plan on place in case Rosecrans did sally from Nashville. Military doctrine is to plan for what your opponent could do, not what you think he might do. In none of the historical record is there any evidence that Bragg communicated any plan of any kind to his subordinates before his ad hoc orders after Rosecrans’ advance.In fairness to Bragg, short of intelligence to the contrary, Rosecrans could be expected to at best spend the winter in Nashville then launch a campaign in the spring. Bragg failed to consider Rosecrans would be pushed to act in December. It is a failure of Bragg's intelligence (the jokes make themselves) to think Rosecrans was starving rather than preparing to attack.
Bragg's flank attack on Dec 31 was an excellent move. It came up short in no small part to Polk's mismanagement of his corps with piecemeal attacks.
Bragg's total clueless about what to do Jan 1 or 2 is a major failure on his part.
David Powell's books give Bragg's intended operations and the reasons they weren't carried out a pretty thorough examination.
Literally anyone. Not removing Bragg after Stones River was inexcusable.
Joe Johnston is the logical choice, both in terms of seniority and circumstances (being on the defensive). When Johnston declined to relieve Bragg, Davis should have responded that he could either follow orders and replace Bragg or be relieved himself for failing to follow orders.
Alternatively, Hardee should have been ordered into command whether he wanted it or not. If not after Stones River then later.