[SalesForce] Is it possible to create a read-only System Administrator profile

Standard Profiles come default with set User Permissions. User Profiles and their customizations are set based on the org type:

In Contact Manager, Group, and Professional Edition organizations, you can assign standard profiles to your users, but you can't view or edit the standard profiles or create custom profiles. In Enterprise, Unlimited, and Developer Edition organizations, you can use standard profiles, or create, edit, and delete custom profiles. For standard profiles, only certain settings can be changed.

Each standard or custom profile belongs to exactly one user license type.

Essentially, these profiles are set up and only some of them allow certain functionality. Not all of the profiles allow access to certain objects (specifically, profiles associated to Portals are very restrictive). This is just how the profiles are set up.

"Since API version 30.0 a change set or ant deployment will fail if a field that is required in the field definition is included in a profile or permission set that is being deployed.

If you create a new custom field and check 'Required', Field Level Security automatically becomes 'Visible' for all profiles. Similarly, if you edit the definition of a custom field which is not visible to all profiles and check 'Required' then it automatically becomes visible to all profiles. Therefore there is no need to reference it in a permission set. Try it!"

It means, that you need to remove from profile metadata fieldPermissions of this field.