Since nobody responded to this thread, I think I'll take a shot.
Keep in mind that I'm not very familiar with the codes you mention, but I
think the "philosophy" behind them is more or lees the same all around the
world. I agree with you about the loads being well known and the magnitude
of the loading factors. However, even if using the factors provided by ACI
318, I'd definitely not forget the impact additional, because its purpose is
to handle the fatigue due to vibrations to which the structure is submitted
when dynamic loads are applied. Perhaps you could use more rational loading
factors multiplied by this additional.
Just my 0.02 cents worth.