I’d argue replacing him is already being done at haste and is being rushed through. Labour need to time to reflect and decide what they stand for before they elect a new leader.
Surely get an interim. Everything he does will be seen as tainted with failure and effectively means no realistic opposition. Not that there is much they can do, but Johnson will laugh at his failure whatever he brings up.
Christ - is Corbyn really going to carry on till March? He'll be destroyed at PMQs (which Johnson might bother to turn up for now).