Your probably right, but things evolve like Mark III influenced the Mark VII at Disneyland and everyone loves them. Certain salutes to the old design should be kept but advancing the concept in more modern design and materials.
To most people the Mark IV is the same as the Mark VI except for the doors.
As you can see the size of the Mark VI is quite a bit bigger where today most people can stand up and travel standing vs sitting. The trains were a huge leap in advanced materials and technologically advanced over the Mark IV's.
Even today the Mark VI's are updated with newer technology, here is the 1990 control panel.
Today's control panel is touch controlled and many times more powerful
I would think the rebuilt for Monorail Purple (or new color) should be a prototype for a Mark VI make over.