[css3-regions] iframe as content source

There is an action on me to add detail to behavior of iframe element when used as a named flow source (http://dev.w3.org/csswg/css3-regions/#flow2)

Here is prose I'd like to put there:
If 'flow<http://dev.w3.org/csswg/css3-regions/#flow2>' property is specified on an iframe, object or embed element the 'display' property is computed to 'none' and the referenced document within the element is used as the named flow. In the case of the object element if fallback occurs and the fallback element has a referenced document then that document is used as the named flow, otherwise the fallback element itself is added to the named flow.
<ins>Any properties set on the iframe/object/embed elements (including margin, border, padding, background) have no effect. This redirection of content does not change representation of the elements in document tree, just as for any other source of named flow; in this case iframe still provides security checks for script in content (and sandbox if required), events and CSS cascading work the same way as in a documents hosted in regular iframes.
Region styling applies to content coming from iframe/object/embed sources exactly the same way as to any other flow content.</ins>
New issue (perhaps this belongs to wiki, not inline with spec):

Issue 5

Having a special case for treatment of iframe box model may be seen as inconsistency in definition of named flows. Also, it may be desirable to add an iframe or object to a named flow as a replaced element (which would require a wrapping element with this definition). This difference in behavior may be acceptable, or it could be addressed by providing an option to use content of an element in named flow vs. using the whole element.

For example, there could be two 'flow-into' properties:


1)    <iframe style="flow-into:flow1"> --  add iframe to flow as a replaced element

2)    <iframe style="flow-content-into:flow1"> --  add content of the iframe to flow

Alternatively, there can be a separate property to specify what to add to flow, with the same effect:


1)    <iframe style="flow-into:flow1; flow-source-type:element"> --  add iframe to flow as a replaced element

2)    <iframe style="flow-into:flow1; flow-source-type:content"> --  add content of the iframe to flow

Note that adding element vs. content option would add interesting possibilities, such as a choice of adding the whole table to flow vs. contributing table's rows into a merged table.