I’m certain it’s a Coldfusion issue as well, otherwise I’d imagine it would have been done by now.
I don’t use shipcompliant (extremely bad experience left a bad taste in my mouth) so I can’t speak to that, but I can see some ways this could be improved without allowing full changes.
Something like “Flip to change order.” A new order is created with a negative quantity amount of the original order, and an additional positive quantity item.
Then, that order would go through full compliance and tax calculations, with any changes in tax or items being charged or refunded as the difference in the original order.
At the end of the transaction, the original order would be set to “no shipping required” and have a flag similar to the “This order has been refunded” flag, with a link to the new order.
This way the net balance would be zero, the customer wouldn’t be charged unless tax or items changed. Compliance would be handled, a record of what happened would be kept. I’d imagine this would be MUCH easier to code than a complete overhaul of the order system.
But that’s just like, my opinion, man.