allow requirements for cli option & arg processing

[fubhy]

What is the problem this feature would solve?

Currently, cli options & args cannot be postprocessed with bespoke requirements beyond the default "environment" (File, Path, Terminal).

What is the feature you are proposing to solve the problem?

It should be possible for commands to carry their R also based on requirements needed for advanced arg postprocessing.

What alternatives have you considered?

No response