I was thinking of something like

#+ATTR_HTML: controls
#+POSTER: quadratic.png
video:quadratic.webm

exporting to the following HTML.

<video controls src="quadratic.webm" poster="quadratic.png"></video>

> That looks too rich for a link to me unless alot of it is always the
> same, or derived, e.g. the id tags.

It is quite rich. But, note that even img tags, especially with the
newer 'srcset' and 'sizes' attributes, are quite rich. Yet, we use links
to insert inline images. If videos cannot be properly handled by links,
neither can images.

> Something like this is what a link would look like:
>
> video:quadratic.webm
>
> and the html export could certainly generate what you put in the html
> block below.
>
> See
> http://kitchingroup.cheme.cmu.edu/blog/2016/11/04/New-link-features-in-org-9/
> for how to make a link, try it and report back if it is useful.

I can use the new link features to develop something that works for my
particular use case. No issues with that. But, I was wondering if a more
general video link type can be developed for inclusion into org mode itself.