You have me thinking about this now.
I don't think you could ever get some sort of "hot water" circulation situation that will do you any good on cold days/short trips. Even if you bypassed the radiator and ran the coolant directly to the trans you would barely have enough time to get things up to temp. That trans will suck a ton of heat out of the coolant. It's a pretty big heat sink.
Now on the other hand if you had some sort of bypass setup that you could switch you could at least heat the trans up as fast as possible and you would also be able to run the trans at a hotter/more consistent temp on longer trips which would improve your mileage. For example, on a 60deg day if you drove it 1hr you could keep the trans at 200deg for the entire trip.
For really cold days/short trips I don't see any solution that is "worth it" aside from using a block heater/coil to pre-heat the case before you leave.
Or you could do both.
