[alatar]

Why so negative on Denethor? He was a man at the end of his rope. His eldest son, whom maybe he had invested much hope, had failed and had fallen. His realm, whether he was King or Steward, was about to be swept away. He was estranged from his other son, the son that may have reminded him of the days spent with Finduilas, the son that he's sent to a needless (seemingly) death. Atop this, should some miracle occur and Gondor withstand the coming storm, a challenge to Denethor's leadership had appeared, and Denethor wasn't one to not get his way.

So he despairs at the end. What if, instead of suicide, someone, like Gandalf, knocks the Steward off of the pyre with a spear (hmm...now where have I seen that?) and he lives, though is mortally injured.

Assume the rest of the events play out as they do in RotK. Aragorn then could meet with Denethor, who, now that his realm as been saved, his son alive and installed as Steward, could die in peace after making some conciliatory remarks to Aragorn, showing that, at the end, he upholds the office of the Steward, giving up command as the King has returned. He asks for forgiveness, it's granted, and Denethor dies at peace, after murmuring some line about joining Finduilas and Boromir and Aragorn says something about the nobility of it all (or something).

Too much like Theoden's end?

Then how about Denethor, like his first son, decides to take Gandalf's advice and lead his people in the defense of Minas Tirith. He can then mutter a few lines and die after some duel with something interesting.