User blog comment:Dragonzzilla/Describe Your Mass Effect 3 Ending/@comment-1786741-20120903230651/@comment-24174486-20120903235717

"Fine then, they destroy the Crucible, which in turn destroys the connected and exposed Citadel. problem solved."

It's almost a certainty that this wouldn't work because the Reapers do try to destroy the Crucible while Shepard is in the Catalyst's presence. Taking too long results in the Crucible's destruction and a non-standard game over. It's unlikely that the Reapers would attack the Crucible if it would put themselves in mortal danger.