A Crimean war mod would play out like NaS with european uniforms.
You can balance it by setting in the 1850's era and adding a faction that still uses the slightly older muskets. You can also give the French and British lines the option of using the slightly older guns with the weapon selection option too. While it might not be 100% Historically accurate it can still be considered fun plus the option is there for those who like to bleed for their fun.
From what I have seen mods set in a single era with only two armies don't last long, I honestly think It would be easier to base mods on eras instead of singular wars and events. You get more interest and can add more content.