Good catch kuroi!!! I had not thought this through enough???

You might review the PCI Compliance rules as if you are using a gateway why on earth would you be storing this information in yourDB or a file?
And check with the gateway as they are supposed to check their user base for compliance...

Not a good Idea to store in any fashion any sensitive data that can be compromised....

If your module does this then all users/host providers must comply with stricter rules regarding PCI compliance