Right now, knowing as much as we know, there IS no harmless choice for them. They can do bad or do worse. They can arrange for the destruction of other Earths, or they can destroy their own, or they can do nothing and let the multiverse continue to contract into nothingness -- and they'll have THAT on their consciences as well, since they know one absolutely effective, sure-fire way to stop an incursion, even if it's horrific. They can't even pat Black Swan on the back and tell her to go back to dealing with it alone, since she might decide 616 Earth should go.
I have a feeling the next issue will show them all researching other ways to stop an incursion and coming to the same conclusion as the Black Swan: there's no way to get out of this once you're in it.