Re: In hindsight what changes would you do
Keep the 8 years after TDK; make it 6 years since Batman disappeared.
Bane was imprisoned in a warlord's pit just like the movie. He was sentenced without a trial.
Bane has been keeping up the the Dent Act since its proposal. He feared seeing the world put into the same sort of police state as he experienced as a child. He hires Selina Kyle, a well-known thief in the criminal underworld, to gather evidence against Harvey Dent.
Catwoman hits up the security archives of the buildings around the location where Two-Face held-up Gordon and his family. She also hits up the security archives of the bar where Two-Face killed that older cop.
Meanwhile Bane and his men head into the Gotham sewers. Its bad; lots of people who would've been paid working for the mob bosses are starving. Watching their children die. Bane gives them a speech and recruits them to his side.
Miranda Tate encourages Bruce to start up a charity for the disenfranchised; now that the mob is gone, white collar crime is the thing. Its hurting Gotham.
Since the Dent Act gave the cops the ability to work in a style similar to Batman, there's lots of frightened civilians. Bane arrives in Gotham in a similar style. Holds it hostage, again. The downtrodden ally with emerging powers in Bane's Gotham; their tasks are to keep the citizens from escaping. Some are afraid of Bane; they try working against him. Other groups of the homeless and disenfranchised try to stop them. They love Bane's plan and don't believe that he would really set off the nuke.
Batman returns; war; Batman appears to die.
"Come!" he roared back. "Come kill me, if you can."