This is a great raspi image. It's really useful for plugin dev work, and I plan on setting up several of these for different purposes / projects. I think this has great potential as a low cost, low power dev friendly environment. On that note, I've got a few suggestions that would make this even grreater (for me at least).
1) How about creating a variety of images? Say one with no plugins, and another with the currently included plugins. Ideally you might even create a set of profiles (eg a base image of just WordPress, a performance image with the currently included images, etc..)
2) Update the image to the latest version of Debian
3) Would it be possible to create a means by which users could customise their image(eg pick plugins to include or set-up passwords etc)
4) Include WP Pusher plugin. This allows you to automatically update plugins from a Github, GitBucket... repo. This is great for theme & plugin devs
5) Likewise adding other dev friendly tools like Query Monitor & Simply Show Hooks, are other near essential tools for devs & designers.