Shipping charges at order level - not line level (dynamic across orders)

Summary:

Question 1:

How to calculate shipping charges at order level based on total order amounts. (could be across orders) for a customer's delivery.

OOTB Line level shipping charges does not work.

Question 2:

we have an idea of creating a freight line item and adding it before shipment in orchestration.

Problem is the revision creation on the order.

with the huge volume of orders - what is the implication of creating order revision during shipment (from orchestration) - performance impact? and unknown issues with orchestration? Since there is a time crunch to calculate and get the invoices ready to go with the trucks, appreciate your inputs.