A silicon diode has a constant voltage drop when forward biased, regarless of voltage applied as long as it is above the .6 or so volt. The voltage across a resistor will vary depending on the voltage applied and will sort of defeat the idea of having the reference voltage to begin with. Withoug digging more into the regulator circuitry, whether or not it will have a similar increase in current is unknown.
If you're going to do it, I'd suggest sticking with the diode. It is not that expensive. Be certain that it is installed in the direction they show in the picture. Diodes are polarity sensitive so they will block the voltage if put in the wrong way.
Black 2000 SSEi, Silverstar Headlights, Angel Eyes fogs, 3rd brake light overlay, hi-flo cat, drilled 180 degree thermostat, Intense FWI, PCM, shift kit, and 3.4 Pulley. Solid front mount.