From 07 service manual:
Exterior Courtesy Lamps
The BCM, driver door switch, and the passenger door switch communicate through the GMLAN serial data system. The driver door switch and passenger door switch supply power and ground to the left and right lamps respectively. When the BCM commands illuminated entry, a command is also sent to the door switches for illumination of the exterior courtesy lamps.
Also:
Driver Door Switch (DDS) C7 (DL3/DR4) - 10 pin connector
[summing up the detailed pin list table] This terminal connection handles the folding, puddle lamps, mirror position sensors
So as long as the wire terminal is already there, it sounds like the door switches just need to be swapped to feed the power to the puddle lamps. Plus that would also give you all the folding/etc options.
Final update:
Upon further research, it appears that this isn't always plug and play. The actual wiring harness for power folding which includes the puddle lamps may not always be there. Any chance you could take a photo of the underside of your door switch? I can compare with mine.