FWIW I wrote a post about this design issue:
Oils Is Exterior-First (Code, Text, and Structured Data) - https://www.oilshell.org/blog/2023/06/ysh-design.html#survey...
That is
- Powershell and nushell have an "interior" design (within a process/VM)
- while POSIX shell, bash, OSH, and YSH have an "exterior" design (between processes)
And I'll claim that the exterior design is the glue you need in large, heterogeneous systems. Making the shell "interior" and "easy to use" is at odds with the role as essential glue -- it creates pressure for something else to be used instead.
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Maybe the more pithy statement is here:
A Sketch of the Biggest Idea in Software Architecture - https://www.oilshell.org/blog/2022/03/backlog-arch.html
The lowest common denominator between a PowerShell, Elvish, Rash, and nushell script is a Bourne shell script (and eventually a YSH script)
I also claim this isn't theoretical -- there are probably a non-trivial number of bash scripts gluing together PowerShell and other shells. IMO it's better to have 1 type of glue, than 2 or more types, which I call "Unix sludge / Cloud sludge".
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And I disagree with this part, which references protocol buffers:
> how do you get a schema? well, you establish in-band communication. RPC is ...
Protocol buffers transmit schemas OUT of band, usually via a monorepo. The data sent over the wire can't be interpreted without the schema information compiled into the binary.
The monorepo works well enough within Google, but even there it failed to scale (probably around the time of "Alphabet", e.g. Waymo and other companies)
Also, protobufs are biased toward C++; users of other languages feel this friction to varying degrees. In general, they'd rather use .gob for Go, pickle for Python, JSON for JS, Java serialization, etc.