It would be very cool, if it were possible to choose between code-files from SD card to install into Arduino. - by pressing input button you can choose between those files and for showing what file is selected, we may use graphical display or some 7 segment dispalys or just led blinking (file no 1 is 1 blink...etc)
Insert SD card to Arduino, choose your code-file and press reset button to upload code to Arduino.