I'venever had a problem with the lack of variety in CS choices because I think of CS as a "utilitarian" meal. I eat it because my body requires fuel, not because its pretty or fancy.
After giving it a little thought though, Disney should be able to replicate any menu seen in a fast food chain. Burgers, hot dogs, foot long sandwhiches, fried chicken, tacos, pizza by the slice, etc... are all viable possibilities. It seems like all you see (with some exceptions) is burgers though.
Huh? I'm not a fan of CS, simply because I want to take a good break from the parks and enjoy being waited on. However, I could easily eat CS for a week at WDW though and never eat a burger. How about:
DTD: Wolfgang Puck Express, Earl of Sandwich, or Cookes of Dublin
AK: Flame Tree BBQ, Yak & Yeti CS
MGM: tough here (Starring Rolls, maybe)
Epcot: Sunshine Seasons, Cantina de San Angel, Kringla Bakery, Sommerfest, Lotus Blossom Cafe, Tangierine Cafe, or Boulangerie Patisserie
MK: Columbia Harbour House, Main Street Bakery, Cosmic Ray's (chicken and ribs)
Resorts: Mara (shrimp or soup), Pepper Market (steak, Chinese or Mexican food), PORS CS (Muffaletta or pasta), or Cap'n Cooks (love their adult grilled cheese)