Including extra CSS/JS to header page level instead of new template

[mvlcek]

Would it be be possible to add CSS ( <link> or <style> ) to the header on a page level, instead of having to create a new template?

You can use I18N Custom Fields or I18N Special Pages to define an additional text/textarea field header for the pages, add the corresponding <link> or <style> into this field, if needed and include it in the template with get_custom_field('header') or get_special_field('header').