"Would it still be a real EF complex type one specifies as the type on the property in such case?"
That's a good question to which I don't know the answer. We haven't done much more than conceptual thinking on this yet.
"I'd like to use the same type for soft relations. e.g. there might be a relation from PurchaseOrder to Customer, but not in the form of a navigational property but rather as a CustomerId property. one would like to use the same type there."
Are you saying that you want only a foreign key property of the key type or that you want a foreign key property of the key type in addition to navigation properties? I think both would be possible but it would still be intersting to know what you are looking for.
Thanks,
Arthur
