Well, it depends on how you do the paper mache. Strips of Newspaper or White/Brown paper and type of glue used, and how thick you do it. Also if you did try to get a smooth texture to the surface.
One problem I see with Paper Mache is that is can get damaged if get too wet but that can be solved with adding a layer or 2 of Clear Coat to create a "waterproof" layers on its surface.
For getting Craft Foam into shape, well, there is the Heat Gun or Hair Dryer.
But I haven't get round to do my Pauldrons for Hades Alone (and his are more "straight") so not too sure how far you can go if using Heat to curve the Craft Foam into shape.
2013 COSTUMES PLANNED
SAINT SEIYA THE LOST CANVAS
SAINT SEIYA SUPER MUSICAL Athena Saori
SAINT SEIYA OMEGA Orion Eden
SAINT SEIYA THE LOST CANVAS Athena Sasha