Would there be any type of cautionary measures if I wanted to build a power LED and Switch right after the AC adapter and before the Galileo Power jack? Most specifically, how much current could the LED consume directly from the Power Supply, the maximum voltage drop across the switch, and if there is any inconvenient in having the LED+resistor line at Galileo Power Input when the switch is off?
I don’t see any problem to add a Switch. Just make sure to test it before you connect it to the Galileo, to ensure that works as it intended this is to avoid any damage to the board, please consider this modifications as on your own risk. Regarding the power LED that is a different story because that depends on the configuration in which you connect the LED and resistor. How much current requires that depends on the model of LED, for that you can check the datasheet of the one you want to use.