Espruino loading source code from SD card?

If you want to load code from the SD card (I guess you want to do this
to allow quick upgrades?) it's as simple as writing a really simple
bootloader and saving that to Espruino:

Would be nice if this feature was built into the Espruino and all a user would have to do is to insert the transflash with the unique user ID with source code and just ground or tie to
vcc a "pre-determined" GPIO pin. No PC required.