IPV/PPV Variance Account Derivation Issue – Drop Ship / B2B PO (SLA)

Business Requirement: For Drop Ship / B2B PO transactions, the IPV/PPV variance account should derive the Operating Unit segment from the Customer Bill-to Site level revenue account associated with the Sales Order referenced in the PO

We would like to have a guidance :

1. Has anyone implemented a similar IPV/PPV derivation requirement in Drop Ship/B2B scenarios?
2. What is the recommended approach to handle such cross-module derivation in SLA?
3. Is there any best practice for deriving AR/OM-based account segments in AP IPV/PPV events?

Any guidance or implementation suggestions would be highly appreciated