Budgetary Control reservation to happen at AP invoice Approval or at GL posting for AP Subledger.

We have a requirement, where Budgetary Control reservation to happen at AP invoice Approval or at GL posting for AP Subledger. The current budgetary control setup allows the choice of reservation point (submit or approve) for Requisitions and Purchase Orders by BU. Payable Invoices BC reservation is during validation only. Validation of AP invoice, reserves funds for invoices requiring budgetary control and places holds for insufficient funds and other budgetary control validation errors. Let me know if anyone has come across this requirement and have any workable workaround on this.