I still have the outline of a story where Delenn turns into Galadriel's Dark and Terrible Queen after John's fall. The Universe regrets it.

I've toyed with similar ideas myself. Because Delenn's two basic reactions to the death of loved ones are suicide and genocide, and sometimes suicidal genocide if she had managed to go through with her attack on Z'ha'dum plan.

I'd definitely say Garibaldi is lucky John survived more less intact, because between Susan and Delenn, the truth wasn't going to save him if it had gone another way.