Adjusting a closed item

We have a number of situations where we need to reverse an older transaction.

We are aware of the unpost process but have issues where, for example, there are too many subsequent transactions and unposting is too complicated/involves too many other records OR where a subsequent transaction is a direct debit payment and is not suitable for adjusting as the direct debit group is too large.

Example - a payment was received and applied OA to an account, this was then matched to a new invoice via the automatching process, a direct debit them collected the remaining balance of the item. At a later date it became clear that the OA should not have been applied to this account. To keep an audit trail we would like to remove the matching and the OA payment from the item but we cannot do this due to the subsequent direct debit (this group needs to be unposted first).