Create or Update a Contact with Tags

For the Constant Contact API POST endpoint "/contacts/sign_up_form" to create or update a Contact, there does not appear to be any way to add/update Tags assigned to a Contact record in that case, as there is with the "/contacts" POST endpoint to create a new Contact. Are there any plans to add support for Tags at the "/contacts/sign_up_form" POST endpoint, or could that feature be added to the API please? I realize it would be possible to accomplish this by running a series of multiple API calls using the GET, POST, and PUT methods at the "/contacts" endpoint to find/check and then create/update a Contact with Tags, but it would be much more convenient and less resource-intensive to have Tags included at the "/contacts/sign_up_form" POST endpoint if at all possible.