Custom version fields should behave as Target Version field does
The Target Version field filters out locked and closed Versions. A custom field of type Version still allows one to see and select locked and closed versions. The locked and closed versions should be filtered out, just as it is for the Target Version field.
Also, would be nice to be able to create new versions from the custom fields of type Version. That is, they should have the same "circle-plus" button next to the field for easy version creation.