Fetch value from child work item

Yours is little complicated. I guess you are looking for rollup count based on a child calculated column.

I tried to understand and mimic your ask as below

• Let us say, orders as epics and order items are Features
• Assume each order item is shipped individually and has milestone statuses => each feature has its own checkpoints.
• Each order item goes through each status like ready to ship, postage prepared, shipped, on the way to delivery, delivered. - - > Feature has similar checkpoints.
• At order item level, You are rebucketing/recategorizing the order item status as started, in-process, delivered. - - > feature checkpoints to Past Due calculation.
• Rollup: Now, you want to status to check at each order level ~ i.e., based on all order items, you would like to know whether the order is delivered, in-progress based on all order items. - - > Similar approach you are doing for Epics by comparing each Features. I guess you are deciding based on any of the child items status i.e., past due calculation.
• I will say that you give weight to the past due calculation values and find a max value of all child items. I am suggesting weight at each item level, which is intermediate step, to know the overall status priority at parent level.
• Based on it you max of child items, assign the status to the parent i,.e. remapping at parent level.

Not sure, my explanation will help, thought of writing my view points. Hope it helps.