tl;dr
Within OrchardCMS, is there any way to automatically migrate the contents of a BodyPart into a LayoutPart? And if so, how?
Detail
I am upgrading an old Orchard instance (v1.8.x) that used the old BodyPart. The goal is to update OrchardCMS to the current release, and with it, migrate to the new Layout system added in v1.9. Enabling the Layout module will add the LayoutPart to content items such as Page, but the two parts both exist on the Content Definition, and moving content from the BodyPart to the LayoutPart seems to be a manual process. Is there any way to automatically migrate content from the BodyPart to the LayoutPart, perhaps even if it was nested within a single Grid->Row->Column(12)->HTML block? And if so, how?
I think you should be able to do this with a little bit of playing around and a little bit of find & replace in your code editor. I would take an empty new site and export two pages, one with content in the BodyPart and one with content in the LayoutPart they way you want it to look. You should be able to see how they are different, I haven't looked at how they export recently, but I think the body part html is contained in a pretty simple xml tag while the layout part includes some code to designate all the elements, with the html contained inside.
Next step is to export all the content from your site (using import/export) and use a good text editor to convert all the body parts into layout parts using find & Replace.
Finally, import the edited file back into the site.
I haven't tried any of this so obviously have a database backup handy and test this out in a dev environment first. Also, I'm guessing that if you follow the directions above you will end up with duplicate content in the body and layout, so you probably want to make sure your import has an empty body tag for each page.