Wow! Never made a cake like that but if I did, I'd stack a couple of layers and shape them into a ' D ' with dowels. Then for the bottom part that s elongated I'd add rice kris pies. Then I d ice the whole thing in a way that would adapt to the shape in the pic. Then I d cover the whole thing with the base color ( the one that s dominant) and add the other colored patters of fondant. For the visor, maybe gumpaste or pastillage with sticks in the part that u will sink into the top of the helmet to keep the visor in place?