We just encountered this issue in a slightly different way. Similar to the example above, we have the many-to-one mapping on "COUNTRY_CODE" on an Address class:

<class name="Address" table="ADDRESS">
...
<property name="County" type="string" column="COUNTY_CODE" length="50"/>
...
<many-to-one name="countryObject" property-ref="code" class="model.lookup.Country" cascade="none" insert="false" update="false">
<column name="COUNTRY_CODE" />
</many-to-one>
...
</class>

<class name="Country" table="COUNTRY" mutable="false">
...
<property name="code" type="java.lang.String" not-null="true" insert="false" update="false" column="CODE3" length="3" unique="true">
</property>
...
</class>

We are actively looking into org.hibernate.type package to try to resolve it. Could I take this ticket to work on it?