If you're asking yourself "what's the point in building another little ARM cluster?" I can totally relate. Answering questions like that is actually what motivated me to begin this project. I've thought about this a lot and written a bit about it here:
This post is a little behind the current state of the project and I've refined my ideas a bit since then, but I think it does a good job of explaining my motivation behind creating the RAIN project and the multiple vectors I'm exploring.