Node-solid-server is just one implementation of the spec. There's nothing stopping another implementation from having a cpanel like management interface.
As much as I like AllegroGraph (and I wrote a book using AllegroGraph) if you want people to be able to install your project easily, then using SQLite, or something similar, might make it easier for people try try it out.
Agreed - the cl-json library will handle all the Solid standards and then developers can layer on top of that their preferred db etc. I'm not sure if we need a db for the core library or not...
