I am unfamiliar with the part in question, so keep that in mind.

We have built USB devices with "multiple identities" before. It's been so long that I can't even remember the terminology. Anyway to the PC it's a keyboard and a generic (vendor defined) USB "thingy". This second interface is what we use for downloading parameter data to the keyboard to make it reconfigurable.

So basically you can add a second Interface/Class/Endpoint(s)/Report to your descriptors. Then do what you want with them.

const char Interface1Descriptor[] = 
{
 0x09,             // length of descriptor (9 bytes) 
 0x04,             // descriptor type     (INTERFACE) 
 0x00,             // interface number    
 0x00,             // alternate setting   
 0x01,             // number of endpoints 
 0x03,             // interface class     
 0x01,             // interface sub-class 
 0x01,             // interface protocol  
 0x00 // 0x05      // interface string index 
};

const char Interface2Descriptor[] = 
{
 0x09,             // bLength
 0x04,             // bDescriptorType
 0x01,             // bInterfaceNumber 
 0x00,             // bAlternateSetting
 0x01,             // bNumEndpoints
 0x03,             // bInterfaceClass
 0x00,             // bInterfaceSubClass 
 0x00,             // bInterfaceProtocol 
 0x00              // iInterface 2 String #
};