As far as I can see, there is not much risk involved in asking Facebook/Google/Dropbox/Yahoo/Microsoft/Whatever to give you "your" data, as per European law. Then look at it and see what is wrong with it. Then file a complaint.

What can they do? It's the law.

Then make the thing public, disclose all your communication with your target, post the story to Hacker News and Reddit, maybe even get picked up by some important blogger or newspaper. Would look good on your resume to fight Google, wouldn't it?

It would look good to be hired for that purpose, and win. Litigious lawyers can easily end up looking petulant, though; if the complaint is trivial or frivolous, the lawyer in question risks being regarded as a bottom feeder. It's better to bring something new to the table, like a winning argument that hasn't been employed before. Of course, I may not be so idealistic in a few years' time :-)