HI, after success with the bootloader with the MK64 (for anyone who seeks for help, see this link) I now understand few other things, obviously, did not think about them earlier (silly me), but better late than never...
My board is far away from the user, so for burning new version, the user has to go back to Bootloader mode, and then burn the new version. Since this cannot be achieved (since the board cannot be reached, so no buttons can be pushed to go back to boot loader mode for the KinetisFlashLoader to connect to the board):
1. can I enter bootloader mode through software? writing something to a register in my user application or something similar?
2. How can I burn new firmware to MK64 through UART? Obviously I need to put some extra code in my application. I guess in such case, boot loader does not have to be installed. Using the UART I will write the new user app to 0x0000 (or some other address) in the flash, so in the next boot, the MK64 will be loaded with the new user app (the old will be deleted from the flash).