The radius of cockpit windows doesn't look that different than the radius on the Comet's square windows.
https://upload.wikimedia.org/wikipedia/commons/2/2e/Boeing_7...
http://www.c-and-e-museum.org/marville/photos/planes/comet-6...
https://upload.wikimedia.org/wikipedia/commons/2/2e/Boeing_7...
http://www.c-and-e-museum.org/marville/photos/planes/comet-6...
Nowadays we have a very good understanding of how metals degrade/respond to repeated load cycles and can design around it. I have not personally worked on airliner window structures but there are a number of avenues that one could take to retain the general shape of the window and still avoid structural compromise due to cracking.