[forgotpwd16]

That's an interesting project to attempt. An issue that should be considered is that pipes can only pass plain text. So every command should import/export structured text which may impact performance and limit capabilities when compared to a shell that can pipe objects.

[csdvrx]

The structure can be done with ASCII: csv and tsv manage to pass data in plain text (the later while remaining readable)

Relational data would have the extra advantage over json-like property-based data of being both easier to present on screen (tables) and to interact with (SQL like: where + order + limit would cover most usecases)