I'm not sure you could have the people of Gotham vote to kill someone without seeming to retread the moral conundrum presented by the boat sequence in TDK.
true but it be alot more convincing than him getting killed because The Joker had alot of power for one man. So if they went that route it would be more realistic plus the people all voted to blow up the other boat anyway and this time the governmet ot political structure of Gotham would make sure of it without the whole moral dilemma.