If all of the data for each field is somehow in the wysiwyg field in some way that it can be axtracted, for example the data for one field is always in a p element with a specific class, and the same of everything else so that it can be reliably extracted, then using something like regular expressions may do it. It would still take a lot of testing and patience. It’s also not something you could run through a browser, it’s something you’d have to set up to run as crons and more than likely you’d have to do it in several passes.
