As I am writing this there no bicycle trousers for urban rain.

It is ordinary, water proof, breathing, rain weather trousers; but totally water proof where the seat is (otherwise water might get pushed through the pants); more sturdy around the knees and front part of the thighs as those parts get more worn. Front thigh should be totally water proof too.

The rest can be the usual breathing and waterproof fabric. But that already exists.
It should be widenable to allow for taking off without taking the shoes off. But that already exists.
It could inherit the idea from jackets, to have zippers in the arm pits, but on the back sides of the thighs.

With my electric cargo bike I can carry only so much cargo. I have an idea about an electric trailer that doesn’t push or help with the forward movement in any way but stay totally neutral. This way there is less chance of breaking any bicycling laws. Let it also have a maximum speed of 25 km/h to surely and totally stay inside the frames of law.

In a very simple solution it can be connected like any other bicycle trailer but it is sensitive to push and pull forces on the hitch. It can have a short play and fast reaction or long play an slower reaction. With the latter a normal PDI regulator might work. Or even a P regulator, albeit with a logaritmic curve. When the tow bar gets pulled, longer, the motor accelerates. When the tow bar gets pushed, compressed, the motor breaks.

It is possible it does not work, that it will play the forces in such a way it will try to throw the bicycle of balance; but why should it? An unpowered bicycle trailer will try to tilt the bicycle as soon as a wheel hits a pothole or one has to break downhill; and they seem to be doing alright.