no need to change the helmet design, just provide different color alternates. A white w/ purple powercat and a center gray stripe with two purple stripes. A charcoal gray helmet with same color stuff as the current helmet.
Also, just tweak the jersey and pants design providing dark gray and black alts like bball. Instead of providing all solid stripes on sleeves and pant legs...on the jersey make the top and bottom stripes out of a dot pattern (like bball unis), and on the pants make the outside stripes out of a dot pattern. Provide some type of "texture" to the numbers and solid stripes.
Edit: Also tweak the Army's black lion logo to make the head look like the powercat and incorporate this hybrid logo some how