The Sweden and other Nordic countries there is a practice of publishing PhD examination reports. Now you may ask who would want to read those, but in Scandinavia doctoral theses in humanities are published as books, sometimes even by commercial publishers, so a report actually works as a book review, with a generous word count of up to 6,000 words. For the new doctors, it may be the only review of their book they are getting. For the examiner, it's a solid publication to add to your CV.
As with turning a conference paper into a publishable article, there are several ways to do it. Since doctoral defence in Sweden is a public event you probably had some jokes in your report to ease the tension. These must go. You also gave the candidate an opportunity to respond to your questions. The questions must now be turned into mild or firm subjunctives: “The candidate could have...” or “The candidate should have...” The examination follows a certain structure, with presentation, bibliography, research questions, methodology, text analysis and conclusion. You can keep this structure, but it will be painfully boring, unless you assume that nobody will read the review anyway (see above).
The written review gives you a chance to say all the nasty things you didn't want to say at the defence because the candidate would not have passed, and that would have given you bad conscience for the rest of your life. But now that they are entitled to put Dr before their names you can finally say what you really think. Although Dr X can still commit suicide after reading the review so you need to be careful. Every “should have” must be followed by “on the other hand”.
The proper way to write a review based on your examination is in fact to write it as if it were a book review. You may use the report as a point of departure, but it has to be re-written completely, re-structured; some clever bits sacrificed because they were side comments during the defence, some explications added since the reader of the review may not have read the book.
In other words, it is quite a lot of work.
I don't have to explain how I am spending my weekend.