an lvt to power a relay is about as minimal as you can get. regardless, using an lvt you still need a stronger power source to send to the relay, and of course the relay needs more power as well to power the lights. not sure if the oem bed light is powered by a relay or the bcm directly. havent gotten into that part much yet.GEN2 def does not have a all the time hot wire in the trailer plug, as i found out when trying to add a circuit for LED buggy whips..
the problem as stated by @FordTechOne is that the Field Effect Transistors in the BCM, or whatever module are only rated to the factory load..
adding 2a with a fuse or not to a circuit only designed for 5a will def cause problems long term..
using the FET/BCM to engergize a relay will add barely anything.. 10mA maybe?