How to make the Work Order and Work Request Status codes more flexible

In oracle standard, whatever user status we define gets mapped to standard system status and the user status behave in the manner corresponding to the system status assigned.

The business requirement is to select a parent status code(mandatory) and pertaining to the parent status code selected, a provision should be available to select reason status corresponding to parent status.

And moreover, we do have another requirement of applying approval rules over these user defined parent status codes and the reason codes too.

Attaching screenshots too for reference.