If you did this, would there be a significant lag from i/o? I assume sticking a Class 10 SD card in it and booting archARM would be pretty quick, but still slower than the SSD that ships with the machine.
Haven't tried on this machine specifically, but never noticed much lag as a result of running from USB on others. There is a USB3 port on the back if you're concerned about performance (just remember this is a $250 ARM laptop, not a MacBook Pro).