eadameg wrote:It looks helpful but in my opinion it would be extremely complicated, because to do that you have to recreate the whole scenario in which the order was done (prices, special prices, discounts, shipping costs, etc.) which might, since then, have changed.
If customer didn't apply coupon code then: Prices are in OrderProductVariant, and that prices on what coupon supposed to be apply. The same about order subtotal discount.
Shipping Costs - here is a bit more complicated as you need to get rates from shipping rate computation plugin.
Definitely to apply coupon code is risky that discounts can overlap each to other if customer service will try to apply wrong coupon code, and applying coupon code is totally resposibility of customer support team, but after meeting with our team they said that would rather have this feature even with risk of wrong coupon applying than not to have it at all.
At the moment I'm creating plugin to apply discount onto placed order, but would be good to have it built-in.