Historical data migration with attachments

Hello Acumatica Community, We have a potential customer who requires data migration of their open and historical transactions. The biggest issue is they require all attachments on each open and historical order to come over as well. Due to the nature of their industry (fire safety) they must be able to store and maintain all of these attachments for life safety purposes should something ever malfunction. We recommended to archive these attachments in a linked folder or site, which was shut down. We also recognize we can use an API push for this which is very cost prohibitive for the customer. Does anyone have any other advice or recommendations?