New cars should look like new cars, not recycled 40 year old designs.
To keep its heritage, it would need hood-scoops or a shaker, a grille with a vertical split, a rear spoiler, and some other minor styling cues that remind you that it's a firebird, without having that recycled design look of the new mustang.
Will it be a coupe, or a hatch? They only had the "coupe" look for 3 of their 35 years.
Is it a continuation from the last generation, or starting over as a "copy" of a first Gen?
IMHO, the early 2nd gens had the best look throughout the years. I'd build off that. It could still look like a "modern" car, yet keep it's heritage.