With the latest 9.6.11, once on an Approach Plate, if you touch the "Plates" button and then enter Full Screen Plate mode, then you will see the route line thinned out and the default is also to remove the instruments too. If this does not work for you, please let us know as there may be a bug.
I don't know if is possible, feasible to thin the route line once it hits the plate area. This is why we did it to the Full Screen Plate Mode. I hope this helps.