Google-drive – Google Drive not downloading any files

This is not doable because of the browser's restrictions since you can't download multiple files in one request and that's why Google (and many other services) is packing multiple files in one zip. I'm not sure if there is any plug-in (I doubt since it's very specific), but what you can do is to install the Google Drive on your computer and all of your files will be always synced, so there is no need to download.

The solution you describe is the best solution.

I personally have "email@address.com" as my top level in my different Google Apps accounts, and I bookmark that page (where I have browsed into that folder) in my toolbar.

This seems to be the best solution for me, and at a glance it is very obvious which folder I want in my other drives.

On a day to day basis, just clicking on that bookmark is enough to get me into the folder that I treat as "root"

You can also use a URL shortener to create links like blah.blah/persdrive that you can then use on public/shared computers where you don't have your bookmarks. I do that for my Google Apps for domains to avoid typing the whole google.com/a/domain.com every time