If my view on what is going on is right, then the radiator fan coming on within 5 minutes of engine start is probably a red herring and not necessary.
A software fix could certainly be applied to handle this better and reduce the incidence of this happening, however, I can't see a way with the current design of totally eliminating it. As a mechanical change, my guess is that eventually, BMW will reposition the radiator temperature sensor / fan switch lower down in the radiator housing so that it closer matches the engine core temperature. If they did that, my guess is that they would completely fix the problem.