To satisfy your requirement, I think the USB DFU can be applied.
When you plug the device into PC, it will enumerate the device as both DFU function and your desired function (HID for example). Then you can run an application on PC to push the device into loader mode.
Freescale USB PHDC stack ver 3.1 has a demo for DFU class.
In this demo, they demonstrates USB DFU class only but not real firmware update application... If you are interested in that, you should contact with their support, they may have a full feature demo.
Regards