Agree, but I don't say that lambda calculus is not interesting, I say that there are so much more alternatives, unexplored. If we do the same with the IC of Lafont, I think that the possible (right patterns) of rewrites (which preserve the no of half-edges and nodes) are about 10^13.

A conjecture, which I don't know if it holds water, is that analoguous to CA, Wolfram style, perhaps 1/3 (or anyway a significant proportion) of the 10^13 possible graph rewrite systems, alternative to IC, are Turing universal.