I don't trust modern writers to pull this off, but at least would establish a framework for the "dark and gritty" elements of a hopeful yet not experienced proto-Federation and how the war shaped the coalition to a larger body of planets united by coexistence and learning instead of conquest.

Here's an stupid idea, if you want to make a dark and gritty Star Trek show/movie that could somehow maintain the spirit and tone of the shows, why not portray the Earth-Romulan War?