Adding input parameters for a standard Fiori app?

Hi experts!

How could we enhance a standard HCM Employee Fiori app, say 'My Leave Requests' to accept the employee as an input parameter instead of simply using the logged on user? We would call the app from some other (custom) app where we have first selected the employee and done some other business logic. This could be some situation where the line manager or assistant has to do something on behalf of the employee.

What would be the correct approach to achieve this?

An extension project to make the initial view accept employee number as an input parameter? Replace a controller totally?

Then continue with the app using that employee as the user instead of the logged on user?

Just playing with some ideas...

thanks!
Ossi M