We thought about that, but it would then require a rework of all animations for each passenger, since a walking cycle with somebody with an umbrella is not the same as a normal walkcycle. And they'll probably have to walk quicker than normal, which cannot be done by just accelerating the animation, because that would result in a silly "silent movie" effect, they would have a completely different walkcycle with a different pacing and stride.
And then, user will ask for multi-seasonal clothing for passengers, which means at least duplicating the passenger variations.
Yes, it can be done, but not quickly.