New feature.

Great plugin, this is my second purchase (3.9 and 4.0), have a suggestion for you though as an enhancement.
When you write the tracking number back, also write the shipment cost back (postage, insurance).
This makes it much easier to calc P/L for each order.
Secondly, update the Shipping address.
A lot of the times the customer doesn't enter it exactly right, and this will help by updating their account.
Thanks Guys!

I can add such feature...

About your request.

1. ShippingEasy has a parameter "shipment_cost".
Did I understand you correct?
Example.
Customer paid you 122$
Iphone 100$
shipment cost 10$
Tax 12$
Total 122$

You changed the shipment method in ShippingEasy with new method with less money 8$.
Do you want to change the shipment cost?
New order amount?

Customer paid you 122$
Iphone 100$
shipment cost 8$
Tax 12$
Total 122$

Ok.
I can't change the order total. I think It's a bad idea.
I spoke with another customers.
Some of them changed the shipment method with new less money shipment method.
But they wanted to hide shipment cost on shipment label.

Can you describe me the your logic?
I can change the the shipment cost.

2. About new shipment address
I can try to change existing shipment address and I plan to add new parameter on plugin configure page.

Is it good for you?

Can you enable debugging on plugin configure page?
Wait several hours/days (I need several shipments) and send me plugin log file.