I'd seen xs before, actually. I spent a while building concatenative array languages (nothing this complex though—file functions! The luxury!) before deciding that I really need some more structure to make sense of the code.
I think there's a conflict between the essence of array languages (building a DAG of monadic (in the FP sense) operations and letting arrays flow through it) and the one dimensionality of a stream of symbols in a text file. Ben Lynn [https://crypto.stanford.edu/~blynn/c/apl.html] puts it best:
"Worse still, tacit hooks, forks, and ranks obscures the beautiful category theory connections: hooks and forks are function composition and application within the Reader monad, while adjusting the rank of a function corresponds to applying functors."
Hooks are a structured approach to this problem, while stacks are an unstructured one. And there will always be tension between the two for as long as the current textual model of programming is used (or maybe no matter what representation we use). How obscure are we willing to get in order to get closer to the beautiful DAG we have in our head?
I of course don't have a good answer to that, and I think the dominant paradigm of array languages has set to be discovered. APL gets us close, but we clearly agree that there's more work yet to be done.
Looking at your bytecode design, I was reminded of this old paper about building APL hardware: http://www.softwarepreservation.org/projects/apl/Papers/1970... . Not sure how relavent that is, but maybe it'll be the inspiration of a beautiful VM architecture!
A good amount of implementation discussion goes on at https://chat.stackexchange.com/rooms/52405/the-apl-orchard . I'm sure we'd enjoy your contributions.