<iframe@srcdoc> property value

Greetings to all.
I had this idea some days ago, while discussing with Ivan Herman about the
possibility of processing an attribute for RDFa. However, that subject was
unrelated to this proposal.

Long time ago I asked WHATWG about how to semantically mark up stuff in an
<iframe@srcdoc> scenario. Namely, I requested whether semantic markup
parsers are required to extract data from elements inside @srcdoc document
fragment, and therefore to parse @srcdoc content. The fact is, @srcdoc
content is something that, once parsed (with entity conversion), resembles
markup and is to be treated as a document fragment. But in order for this
to work, a user agent must know the subtleties of such an attribute.

I received no answer for that, but still I realised that it was pointless
because markup *inside* @srcdoc has no meaning on its own. Rather, all the
content of @srcdoc can be relevant as an object (a comment, a review, an
external integration to an article, etc.). In this case, I guess that an
RDFa property specified on an <iframe> should refer to that content in
first analysis, and treat @srcdoc value as it would with a property with
value identified as XMLmarkup-typed literal (datatype="rdf:XMLLiteral").
This would be useful in all cases where @srcdoc matters, and even more
useful for fans of RDFa Lite (as I am), who choose not to use @datatipe and
therefore can never benefit from identifying content and markup as property
value. Finally, it's perfectly backward compatible as authors who use
@srcdoc are suggested to use @src for legacy compatibility, while the
former always takes precedence over the latter. The rule would be the same
for HTML and RDFa: the parser should consider @srcdoc as property value if
compatible, otherwise it would use @src.
Is this viable?
Thank you for your patience
Andrea Rendine