[megapatch]

This is already implemented, modern bash offers completion and suggestions, which look exactly like shown (text only though) when you press Tab.

This includes parameters, flags (with documentation), context (eg files in current directory).

Autocomplete is available for most commands on modern Linux installations.

[eequah9L]

Bash is apparently capable of showing the completions with explanations, however there doesn't seem to be a de facto standard way of doing it. Or did I miss something? Are there like libraries to help out with this, so that the help text is shown consistently?

But yeah, agreed that pursuing this path would be less effort and get 90% of the way to the goal.