Yesterday I attended an ASJA (American Society of Journalists and Authors) workshop on ghostwriting. It sounded interesting and it was free, so why not. Listening to the speakers on the panel, it occurred to me that American experts who are not good at writing aren't the only ones who need a ghostwriter. America has any number of scientists and other experts who came here to study and stayed on or arrived after completing their studies elsewhere and remained. Depending on the person's background and subject matter, they may or may not be highly proficient in well-written English.
There are famous fiction writers and journalists writing in English whose first language wasn't English -- but there are also scientists and other experts who grew up elsewhere, are highly proficient in the English vocabulary of their specialty, but not so great at communicating in English with a wider audience. It seems to me there is a niche here for bilingual (or multilingual) people who write well in English. When I asked about a market for that particular niche at the workshop, I was told that this was something to be explored. Later I was encouraged to put together a network of translators-ghostwriters for different languages.
One of my projects quite a while back was a combination translation/editing job, where an Austrian non-profit had run a project with high school classes in various countries. The students were communicating in English within the project and the teachers produced reports on their activities in English, as well. However, since this was a social studies project, some of the teachers involved had limited English skills. It fell to me to edit the English-language reports and to translate the ones from Austria (which had been written in German in the first place). The fact that I spoke Spanish and French turned out to be quite helpful when editing English-language reports from Latin America and francophone Africa. When the text was unclear I could basically "re-translate" it back into the writer's dominant language and thereby deduce the intended meaning.
It seems to me that ghostwriting in English for experts whose first language is not English, but who nonetheless know their subject matter mostly in English would be a similar process. For that reason, it would be helpful to such experts to have a ghostwriter who speaks their dominant language. I don't know how many German-speaking scientists or technicians might be interested in writing a memoir or popular science book on their specialty, but it does sound like an area worth exploring. Now if any other translators out there are interested in ghostwriting, maybe we can put together that network ...