Allow Customizable Field Explanations and Descriptions Merged

What is the challenge?

Currently you can add a "field description" for custom fields, but not hard-coded existing fields. Admins should be able to add a description at every level.

e.g. the Status field on Initiative. Want to inform users that the Status field should be set to Green when X parameters are met, Yellow when Y params are met, and Red when Z params are met.

or

As we are using Roll-Up Initiatives, a grey text at the Product level so that when a user tries to create an initiative at the wrong level, the description says "Do Not Create Initiative at Product Level. Initiatives are Created at Product Family and Product Line levels"

What is the impact?

Custom Layouts, Existing Fields, Custom Fields.

Describe your idea

Allow the ability to put in field descriptions on existing and custom fields. Also allow the ability to manipulate the grey text in a field that requires input.