Alternative to Reporting Ledger to report in 1 Currency?

We have about 50 organizations, Operating Units and Ledgers. The majority has EUR as functional currency with a few exceptions (Companies in US, UK and Australia, for example).

There is a need to be able to report all transactions (AP Invoices, PO's, Manhours, etc) for a certain group of projects in various ledgers, in EUR.

One way of achieving this could be creating Reporting Ledgers at Subledger Detail level.

However as most of the ledgers already exist this might run into issues with creating the historical data.

In additions, this implies more ledgers to control and monitor, more periods to open and close, new data access sets and responsibilities. etc etc.