Til and I and Jeff Davis has discuess this on IRC. package_instantiate_object almost does this, but using it is not as straightforward as Til's suggestion. Here is what we came up with today:
db_plsql -package bookmark \
-operation new \
-args {
object_id $object_id
name $name
content $content
}
where args contains a list in array get form of paramter names and values.
To make this work, functions in postgresql would need to be definied with define_function_args plpgsql procedure to capture the necessary parameter names and default value information that is build in to oracle.
