webcomponents: <import> instead of <link>

Just after started prototyping HTML Imports on Blink, this idea comes to my
mind: Why not have <import> for HTML Imports?

The good old <link> has its own semantics which allows users to change the
attributes dynamically. For example, you can change @href to load other
stylesheets. @type can be dynamically changed as well.

In contrast, importing HTML document is one-shot action. We don't allow
updating @href to load another HTML. (We cannot do that anyway since there
is no de-register of custom elements.) This difference will puzzle page
authors.

And an implementer (me) is also having troubles... Current <link>
implementation is all about dynamic attribute changes. disabling its
dynamic nature only with @rel="import" seems tricky.

Well, yes. I can just refactor the code. But this complication implies that
making it interoperable will be a headache. There will be many hidden
assumptions which come from underlying <link> implementation. For example,
what happens if we update @rel from "import" to "style" after the element
imported document or vice versa? We need to clarify all these cases if we
choose <link> as our vehicle. It seems burden for me.

Using new element like <import> doesn't have such issues. We can just
define what we need. Also,
we'll be able to introduce import-specific attributes like @defer, @async
or even something like @sandbox without polluting <link> vocabulary.

One downside is that we'll lose the familiarity of <link>.  But having
indirection like the "Import" interface smells like we're just abusing it.

What do you think? Is this reasonable change or am I just restarting
something discussed before?

-- 
morrita