Here is a quick thought I want to put into your head. There are so many ways to do just this in Maximo, but what are the best ways and what are the affects of doing it a certain way?
Database Configuration
If you make a field required in the database config, it will be required at the object level and anywhere that field is used in Maximo, it will stay required, even when used with MIF.
Application Designer
If you choose this route, the field is only required within that specific application you set it for. Maximo will only check if the field is required only when a user is in that application. It will not check when being used with MIF.
Conditional Expression
Choosing this route is the same as going with the application designer.
Automation Script
Since Automation Scripts are used to manipulate business objects, it can be used to make fields required even thought it maybe not the most ideal place to use it. If you make a field required at the script level, it only does it based on your script. Using it this way can also trigger when used with MIF.
UPDATE:
Global Data Restrictions
Making a Field Required for Everyone in Maximo using Data Restrictions
Using a Data Restriction to make a field Conditionally Required by Security Group
