Had an interesting chat with Greg about said topic and searching showed the following link to discuss this topic in some detail (no reason for me to repeat this).

insert /*+ noappend parallel(t1) */ into t1 select /*+ parallel(t2) */ * from t2 generates a load table conventional and does give you a parallel insert without doing a direct path insert.

As this is missing from the official documentation it is probably something few people actually know existed, so kudos to Randolf Geist.