How to extend simpleType string to add new value (enumeration) ?

Question

i have multiple schema files :

base.xsd

<xs:simpleType name ="PropertyNameType">
    <xs:restriction base="xs:string">
      <xs:enumeration value="UniqueID" />
        <xs:enumeration value="Name" />
    </xs:restriction>
  </xs:simpleType>

Now how to add enumerations list to same type in A.xsd

<xs:redefine schemaLocation="base.xsd">
    <xs:simpleType name ="PropertyOutputsNameType">
      <xs:restriction base="PropertyOutputsNameType">
        <xs:enumeration value="Description" />  
        <xs:enumeration value="Value" />
      </xs:restriction>
    </xs:simpleType>  
  </xs:redefine>

The enumeration value above is not worked, but :

1) I dont want to write new type, because the property is so many. In scenario of inheritance and need to use 'redefine' feature

2) But the limitation of xml schema that can not extend simple type from base simple type, only using restriction not extension to add new enumeration

How to solve this problem ?