Well, I'll just input most of my thoughts here in how I would have personally changed the film:
1. I would have made Bane his own man in the sense where he shared no personal connection or ties with Talia in any way. I would have had him be the child that escaped the pit, and that he was in charge of his own private military that was responsible for several regimes falling across the world. Talia would have sought him out to strike a deal, one that she believed that Bane would cooperate with her, but in actuality, Bane would double cross her as well. Bane's goal would have been to either cripple the US starting with Gotham or break it apart so that he can establish his own regime there.
2. Instead of focusing so much on the orphanage, I would have had some scenes dealing with how Gotham's Citizens were reacting and responding to Bane's hold over Gotham, let alone on their thoughts about Batman before he returned, when he was defeated, and when he finally returned to defeat Bane once and for all. That was sorely missing in this film, especially when Gotham's citizens were established so well in the previous film.
3. I would have had Talia reveal herself much earlier on, with her identity having been known to all during the 5 months. Her goal could have been not to destroy Gotham but to literally go through its corrupt and execute them one by one during the 5 months, with the bomb as her way of insuring that no one from the outside interfered.
4. Gotham should have looked much more worse than it did during the 5 months of militaristic rule from Bane.
5. I feel like they should have filmed the final battle/so called war between Bane's mercenaries and GPD much more better, more intense, and have the entire people of Gotham involved.