Auto Create User from Ticket-API

Oh yes, please.
We have an own “Create new ticket” form in our application and are jumping through the following hoops to create a ticket:

Check if user exists 
GET /api/v1/users/search?limit=1&query=email.keyword:potentiallyNewCustomer@example.com X-On-Behalf-Of null

if not exist, create it
POST /api/v1/users X-On-Behalf-Of null

create ticket with the user.id of the new or existing user from above:
POST /api/v1/tickets/ with X-On-Behalf-Of: user.id from above

Would be great to just do it in one shot.
The newly created ticket should belong to the customer (by email).

Initially I would have had expected that X-On-Behalf-Of would work like this, but it fails if the user does not exist yet.