models.py

class LatestVersionManager(models.Manager):
    """
    Return only the latest version of each model in its default query set.
    
    Subclasses must define `version` and `id`.
    """
    version = 'version'
    id = '_id'
    
    def get_query_set(self):
        table = self.model._meta.db_table
        
        where = """{table}.{version} = (SELECT MAX({version}) FROM {table} AS sub
                   WHERE {table}.{id} = sub.{id})""".format(
                        table=table,
                        version=self.version,
                        id=self.id)
        return super(LatestVersionManager, self).get_query_set().extra(where=[where])

class MyModelManger(PassThroughManager):
    def my_method(self):
        # do some stuff
        pass

class MyModelQuerySet(QuerySet):
    def my_method(self):
        pass

class LatestMyModelManager(MyModelManager, LatestVersionManager):
    pass

class MyModel(VersionedModel):
    objects = LatestMyModelManager(queryset_cls=MyModelQuerySet)
    all_versions = MyModelManager(queryset_cls=MyModelQuerySet)