[whatwg] [web-apps] Ability to treat transparent part of element transparent to events

See:
https://bugzilla.mozilla.org/show_bug.cgi?id=102695 - Treat some 
transparent elements as "transparent to events"
I think that explains basically what I would like to have.
Afaik, that's something that IE is already doing (at least I heard).
Basically, I was thinking about some sort of attribute that would enable 
this behavior.
Is this something worth considering for the Web Applications spec?

Regards,
Martijn