Have you come across any other interesting resources? I've recently been delving into topics surrounding echo state networks for my thesis, so I'd appreciate any pointers.
That said, it's pretty marginal stuff. ESNs are weird. Cool weird anyway.
If I were looking at it in a serious way rather than reading the funny papers, I'd think about ways of applying topological ideas to ESNs. ESNs on the critical ridge probably have an interesting graph when projected onto a topological space.