Create eMMC Flasher that flashes the bootloader also?

I am happy creating an eMMC flasher that flashes the eMMC but is it possible to create a version that takes the current bootloader and flashes that also?

Are you flashing through USB or via SD card?

Via USB, you have /dev/sdb access to the entire eMMC device, and you can put whatever you want onto it.

via the SD card. My thoughts were if the script can do it why can’t the eMMC flasher?