I could be of great value if it was possible to appand the analytics data from the users session the contact API. At the moment this can only be done with the Forms API, but that is not very flexible in that you need to create a form in hubspot that is 1:1 with the one you are sending data from.
When building an intergration to Hubspot that creates contact the analytics data would be great to have so you could better see where the user was created from and how.