Allow occasional non-referencing values

It may often be desirable for referencing fields to contain not only references (i.e. nid numbers) but also free text - for those referenced values that do not exist yet. One could then use Views to select all non-existing values in the referenced fields and fill them in (or, in case of titles, create new nodes). And next time the referencing node would be saved it would contain the nid, not the text anymore. Any ideas, plans?

Currently something like this is possible with content taxonomy autocomplete - one can type any value and it will be created - but that is not a perfect solution (no notion of non-existing values as I describe above, having the overhead of the complicated taxonomy system, etc.)