Impact of making fields mandatory in Employment Page

Summary

What is the impact of making fields mandatory in Manage Employment Page

Content

Hi Team - I have a very basic question about making few employment fields mandatory , ex : Grade, Line Manager, HRBP etc.

There is a business requirement to make these fields mandatory as its needed for the downstream applications. We were able to make these fields mandatory, but there are many employee's who do not have values updated in past against these fields in the past (their historical records have blank values against these fields). So now if I make these fields, would it have any impact ? Are such records with blank value prone to errors?