well I still adamantly believe that having an element directly inside the oil pan, directly touching the oil, will be the trick. I'm not too worried about boiling the oil because it wont be on the hottest setting. It's pretty hard to even boil cooking oil with the large elements deep friers use.
2 minutes with that type of setup, and your oil would be really really runny, easily flowing into spots it would not normally flow to under cold conditions. Hook up a remote control to turn the system on and make it more efficient. By the time you get to your car, your oil is pre-warmed.
i like that gear driven oil pump, but you still need to get a motor to drive it... could possibly use a cordless drill i suppose, but a lot of work.
black smokin diesel, i strongly suggest you get a marine battery and an isolator. stick the marine battery in the back, and use that for your heating purposes. its not a wise idea to draw from your cranking battery like that... on really cold days you'll need all of the cranking power you can get to turn over your cold and cranky motor.
once i get an oil pan to do some experiments in, i will see what works/doesnt. and find some sort of timer for the remote system.

and i may even just use the element from a hot water kettle. remember that we don't need to 'boil' the oil, just bring it up to around 5-10C to lessen the wear.
it wouldn't even be a bad idea to heat up the oil in the spring/fall temps or cold summer nights either.
BTW I have peltier elements that are 350W rated... wonder how they would work..

only good till around 100C though... But they could generate electricity from the hot oil pan hehe