Timon, your side seating suggestion makes sense in that more passengers could fit inside (with the extra standing room in an "open" floor plan). I'm sure your idea will generate some interesting discussion, as many people enjoy and appreciate the monorail.
Yet, IMO, I think I still like the current style with the middle seats—it creates a bit more of a welcoming design feature. The monorail is more than just a means of transport; it's also always been an attraction within itself. Maybe in some respects, the present theming has cut down on the number of passengers that can fit in each car, but I still tend to gravitate toward the middle-seat design from an esthetic point of view.