The statement: "force can be used for battles throughout the period" Is either false or true for everyother period in wargaming.
Every single nation went through at least one major uniform change.
Austrians are easiest, only headgear change for infantry and cavalry mostly stay the same.
British had minor change to infantry(bigger for officers)
But their cavalry went through MAJOR change.
French, had 3 major uniform changes for their infantry,
Dragoons and chasseurs had a major uniform change.
Hussars had several headgear changes.
Carabiners totally different uniforms.
Guard cavarly also had changes.
Artillery had changes both to uniform and guns.
Prussians in 1806 vs 1813 are completely different, the only thing that hints at them being the same army is the use of dark blue coats.
Russians had major change from 1805-1807 vs 1809 then a smaller change after 1812.
Yes you can use bicorne French for Waterloo, but then you can use republican Romans as empire legioneers
or surcoated knights for the 1st crusade, or early war germans for late war germans in WW2.