Increasing the gap between web and publishing or unifying them?

Dear colleagues,

The whole point of the unification of IDPF and W3C is to
unify the web world and the publishing world.  But I am wondering
if we are rather increasing the gap between the two worlds.

See

https://github.com/w3c/publ-cg/issues/11

I think that we should not

1) Create an EPUB-specific CSS extension
2) Introduce more FXL metadata

People appear to agree that 1) is bad.  But I think that
2) is also equally bad.  Remember that some FXL
metadata  (e.g, rendition:align-x-center) has not been
widely implemented.  Even when they are implemented
in EPUB, the OWP does not have equivalent features.

I would like to recommend two actions.

First, we  should provide a detailed prioritized requirement list
and request the CSS WG to address them. Paged media should
be top in the list.  A recent submission [1] by Vivliostyle is hopefully
useful.

Second, we should study EPUB features (e.g., media overlay)
missing in OWP, and request the entire W3C to address them.
See my list [2] of such features.

Regards,
Makoto

[1] https://www.w3.org/Submission/2017/01/
[2]
https://docs.google.com/document/d/1MY_qIkT8AD6m-M4mEUy7dr3jTH56Eiafdj6E2X6FsIQ/edit