I am working on a subscription-based project and I am looking for a way to store card information data in case I would be switching my payment processor provider to another one. In which case I would have to force all users to re-subscribe which would most definitely cause a massive loss of revenue(at least initially). So by having access to the card data I can "upload" card data into the new payment processor and continue operations without outage.
What would be a good way to approach this that would not bankrupt the project from the get-go(ie. PCI DSS certification and infrastructure costing hundreds of thousands of dollars)?