The super easy way to do this is to partition SD cards. I'm assuming a partition table would be required and limiting to 4 partitions maximum on a single SD card. If logical partitions can be used similar to a HDD, the sky is the limit. I vaguely remember the PS3 used a work-around for this on...
Shawnita used to get her pills from some other street pharmacist and after switching to The Psi Discount plan she now only has to swallow two things a day!