We have a client that uses multiple ERPs, handles payments differently for different items, and has complex shipment logic. This forced us to break up our orders in to multiple order forms with multiple shipments. Everything has worked well with the exception of discounts that need to be facilitated/calculated across multiple order forms like whole order discounts when a threshold is met. I've been looking in to the logic changes it would take for OrderGroup level, and they seem pretty extensive.
From what I gather, I would create our own processors which look at the entire OrderGroup, and may need to implement our own version of the promotions for item specific forms, since we don't want to apply rewards in multiple order forms some times. I'm worried what this might mean to maintain, and how long it might take to implement. Has anyone else managed to do something similar. Is there a better way to implement promotions over multiple orderforms?