Hi,
I'm not a taxi driver, but I do carry passengers and they often have the same problems.
Mine's an '03, which means that the easiest way to release the door from inside is to use the far arm, cross it over the chest, and so get a better push on the relase button. Pasengers instinctively use their near arms and then can't depress the button properly. Explaining this is not easy and so I tend to hop out and open from the outside.
The latest revised models have a completely different mechanism,. This has a properly ergonomic handle which has an easy trigger release from inside. The door locking/sliding mechanism is improved too, with a spring door release (when open) which demands that the open door is tugged away from the body of the car before it is slid. Instinctively one pulls and slides at the same time, but this won't do.
I have to say that my doors open more easily from inside than they used to.
However, you are right about trapping fingers. Just tell them to be careful to only hold the handle and watch keeping their other hands anywhere near the door opening.
I asked my dealer if it was posible to upgrade and was told no. This is not just a simple change of fitting but a slightly more serious bit of engineering.
The rear wiper on the latest models is a better design too! That you can change.