After reading a post be someone who deleted a site then wanted to set up a redirect I looked at the help pages and dashboard pages and I think they could be made clearer. I suggest that
1) The "Delete Site" support page has a list after "If that’s not what you want to do, you can instead:". I would suggest that you would add "Redirect the traffic from your blog to another site" to this list, linking to the Site redirect support page.
2) The drop-down in the dashboard when you try to delete a site (under Delete Site: What is your goal?) should also have the option "Redirect traffic to another site". Selecting it should then take them to the Site redirect support page again.
I think this would be helpful to users who may not know of this option, or who do know about it but assume that they will be able to set it up after deleting the site