There is no simple "consolidate library" option, nor any plugin I'm aware of that will manage this for you.

As you no doubt know, Lightroom doesn't care where you store your files or what sort of directory hierarchy you might use (if any). In other words, moving these files is for your own satisfaction only. 30k files in one folder could be a performance hit, but otherwise I don't expect you'll see any performance change after moving files, either.

I suggest that the best and easiest way to do this is to bring a little organization at a time: Use the Library filters to find all photos in a given year (the metadata filter makes this easy). Within Lightroom create a new folder for that year, and drag all photos (previously selected) into this new folder. Repeat for each year you have photos.

You've now got a YYYY/file.ext hierarchy. The photos are now much more organized! Personally, I would consider this done (or a task for some lazy time) and not worry about further historical organization. Going forward you can import to a YYYY/MM/DD structure. Remember, Lightroom does not care that your files are only in YYYY folders, so the only benefit to taking this organization further is if you've got a very large number of photos in a single year where performance could, potentially, be impacted.