Feature Request: Combine functionality for shipping options

[meandillar]

Feature Request
Allow modification of Shipping Option UI targets from within a Delivery Customization function.

Our use case
We are transitioning from checkout.liquid and Scripts to functions and UI extensions as mentioned in #299

We need to:

• Hide irrelevant shipping options based on customer zipcode
• Rename shipping options according to the current time, based off some "shipping cutoff times" (for example depending on the shipping cutoff time the option title could display as "Same Day Delivery", "Next Day Delivery" or "Next Working Day")
• Display estimated delivery times as a subtitle
• Discount the shipping rate based on customer tags

To achieve this we'll currently need to use:

• a Delivery Customization function
• a Shipping Discount function
• a Checkout UI Extension for adding shipping estimates and other info to the 'purchase.checkout.shipping-option-item.render-after' target

Problem we've encountered
We have delivery zones that are associated with groups of zipcodes. The titles of our Shipping Options set in Settings -> Shipping and delivery include zone info (for example 'Zone 1’, ‘Zone 2’) that is used to do 3 things at checkout:

• hide irrelevant zones in relation to customer zipcode
• rename shipping option title to reflect the type of delivery (Same Day, Next Day, Standard, etc) based on zipcode and shipping cutoff times (configured in a shop metafield)
• display delivery estimate below the title based on the zone and shipping cutoff times

The problem is that we can't access the original Shipping Option titles in the Checkout UI extension because they've already been modified by the Delivery Customization function, so we're no longer able to determine which zone we're dealing with in that particular shipping option and therefore unable to display the relevant shipping time estimate.

If there is another way to access the original Shipping Option title I'd love to hear :D

Other reasons why we'd like this combined functionality:

• Solves issue of sharing configuration data from shop metafields between the Delivery Customization function and Checkout UI extension (raised in Access shop metafields #299)
• Means we wouldn't need to maintain both a function and an extension for affecting Shipping Options.

We can make it work currently but it involves adding extra logic to figure out which zone correlates with the current shipping option and executing 2 lots of similar code (once in the Customization function and once in the UI extension) which feels inefficient.