I concur with the need for a better solution than the arm rest holders; however, one needs to consider...

If the cup holder were installed on the door panel, there is the ever present possibility [especially with kids] that, when the door is either open or closed, whatever liquid is in the door-installed cup holder, will inevitably [sometimes violently] splash upwards, outwards, and sometimes with trajectories that could make many Nobel laureates choke on their tofu. It is/are the latter types of event[s] that cause those "unexplainable" spots on the headliner, sticky switches, and the ever popular "okay-mister,-explain-this-one" stain[s] on your clothing [this does indeed happen, ask former President Clinton].

For me anyway, I don't mind the cupholder in the center as I seldomly ever have to control the rear windows with the same frequency at which I use the holder, I would just prefer a more robust [yet simpler] design.