Dynamic @action attribute on xforms:submission

All,

With XForms 1.0 and 1.1 draft, it is not possible to dynamically
specify the @action attribute on xforms:submission. However, in these
days of REST, it is obviously necessary to be able to do that.

How have implementors addressed this? The following solutions come to
mind:

o Handle @action as an attribute value template, for example:

   action="http://example.org/app/{instance('my-instance')/image-name}/etc"

   Benefits: very flexible; XSLT does it so we are not reinventing the
   wheel.

   Drawbacks: XForms doesn't use attribute value templates anywhere at
   the moment. Users will expect that avt will work in other places as
   well!

o Extra attribute on xforms:submission, such as @action-ref.

   Benefits: does not introduce avt.

   Drawbacks: another attribute to remember; requires @action to be no
   longer required; doesn't scale to other attributes; *-ref attribute
   names are not nice-looking ;-)

Any other ideas or suggestions?

-Erik