MIOS is just the operating system so you need to upload an application as well. This is also handled by the bootloader. As each part of the MIDIbox software is stored in a particular location on the PIC, I don’t think it will work without the bootloader as that is what starts your application (if it doesn’t receive a response to it’s upload request)
Also MIOS Studio gives you a very easy method of uploading software to your MIDIbox and simply needs a MIDI IN and OUT connection to the CORE.
Thanks
Phil
EDIT: In case I wasn’t clear enough, the bootloader is NOT optional