SIP Header options for Skype For SIP

With Skype's "Skype For SIP" service at http://www.skypeforsip.com/ one question several of us have had is this: can we get the same headers in SIP that you can currently get in Skype For Asterisk?  Those headers are:
   
    * skype_languages - A space-separated list of language identifiers (ie - es, en, etc)
    * skype_topic - A user-provided string that can identify the ‘topic’ of the call
    * skype_token - Similar to skype_topic
    * skype_about - ‘about’ profile entry
    * skype_birthday - Birthday
    * skype_gender - Gender
    * skype_homepage - Home page URL
    * skype_homephone - Home phone number
    * skype_officephone - Office phone number
    * skype_mobilephone - Mobile phone number
    * skype_city - City name
    * skype_province - State/Province name
    * skype_country - Country name

With these you could do some interesting call routing.  The question back from folks at Skype was - so what headers would you want these to be mapped to?  (Not committing they'd do anything, but just asking.)

None of these really appear on: http://www.iana.org/assignments/sip-parameters  so this is just a space to work out some ideas. Obviously you could just prepend "P-" to each and make custom SIP headers such as "P-skype-languages", but the ideal would be to find *existing* SIP headers that could be re-used.   Here's the list:

skype_languages   ->
skype_topic       ->   Subject 
skype_token       ->
skype_about       ->
skype_birthday    ->
skype_gender      ->
skype_homepage    ->
skype_homephone   ->
skype_officephone ->
skype_mobilephone ->
skype_city        ->
skype_province    ->
skype_country     ->

Suggestions are welcome.