Keeping all cards on file when merging records

Merging records is something we cannot avoid doing, and every time we have merged records, it triggers something weird for the account. 

Can you at least make sure that merge feature allows us to keep all credit cards in both account that are being merged? This allows us to select which card can be used for next charge. 

In addition, we need to be able to select what info can survive on the new account and what gets discarded. This is really important. Like which campaign the surviving account can be part of.