Turn a paid WooCommerce order into a shipping label automatically

A store owner describes their process like this: "When an order is marked
'processing', I want a shipping label generated automatically through ShipStation
using the customer's shipping address and the order weight, the tracking number
emailed to the customer, and the order status changed to 'ready to ship'."

AVAILABLE TOOLS: [WooCommerce (trigger), Uncanny Automator, ShipStation, WooCommerce
order emails]

Turn this into an implementation-ready automation recipe, thinking through what the
plain description leaves ambiguous:
1. Trigger: the exact status-change event to fire on, and whether orders that skip
   straight from "pending" to "completed" (common with manual bank transfer payments)
   should also trigger label creation, since the plain description only covers
   "processing".
2. Conditions: what happens when ShipStation's address validation flags the shipping
   address as undeliverable. Should the recipe halt and notify a human, or generate
   the label anyway and let the carrier reject it.
3. Actions in order: pull weight and dimensions from the order items (accounting for
   orders with multiple package-requiring items that don't fit one box), request the
   label from ShipStation, attach the tracking number to the order, then send the
   customer email, in that order so the email never goes out before a tracking
   number exists.
4. Failure handling: if ShipStation returns a rate error because a product is missing
   weight data, should the order stay in "processing" for manual handling, and how
   should that be surfaced to the fulfillment team without an email misfiring to the
   customer.
5. One edge case specific to this exact workflow: a partial refund or item removal
   that happens after the label was already purchased. Decide whether the automation
   should attempt to void the label or leave that to a human.

Replace the workflow description and available tools with your own.