I've only scratched the surface of Xonsh, so please correct me if I'm wrong.
From what I understand, Xonsh was designed as a "readline shell" as I wrote in the article. It perpetuates this approach that everything is a command.
The thesis of my article suggests we do the opposite: I'm suggesting to rethink shells by starting from the interface (here the SLY REPL) and then implement the shell features. In particular, it seems that Xonsh does not support back-references and I'm not sure it has an interactive inspector (or does Emacs python mode provide one?).
While Xonsh seems to be a definite improvement over the syntax of Bash, etc., I'm not sure it brings much novelty in terms of user interface. But again, I know very little about it so I may have missed some features, in particular regarding the Emacs integration :)