migrating project budgets creating current working version

Summary: Client will migrate project budget information. The migrated project budgets will require to automatically create a current working version of the budget. The reason is that we upload the original budget and the subsequent budget changes in a second load. The second load will (aiming for) processing mode Update. What are the options to load the initial budget and second budget load? And what are the relevant fields to take into account when loading these files? Currently workflow approval is enabled for the relevant financial plan type, but can be disabled if required.

Any ideas or options for this topic are appreciated.