It would still be more appropriate to up the strength/boost on the SHO engine and put it in a Mustang SVO edition instead of another Shelby. Make it optimized for weight distribution again plus clean lines (no stupid plastic crap). Shelbys are nice and heavy and brute force but the SVO was fuel efficient and balanced. Just my $.02
I think Ford has 2 routes to go. And these routes are defined by demand and by the ever-increasing EPA ridiculous standards.
1. Keep V8's in the Mustang while achieving crazy MPG figures with other vehicles (Focus electric, C-Max hybrid, C-Max electric, Fiesta, etc...) to reach the EPA's lofty mandates.
2. Introduce Ecoboost into the Mustang....and still have vehicles with huge MPG figures.