Yes you are correct about the value of Duane's work. The fact that he was a favorite of Jefferson and Madison did mean that his work was read. In fact the 1810 uniforms are predominantly his design. Whether you like it or not I don't think that the existence of his efforts can be dismissed due to better efforts in existence. It was used and it did survive the war even with its' shortcomings. Thanks in large part to the fact the General Smyth was such an idiot that the Army simply erased him from their roles as if he didn't even exist. Even Hull was handled with more formality.Smyth has the distinction of being the only US General in History to simply disappear, no retirement, no resignation no nothin'. We should remain complete when describing the governing works of the Army.
There is a little known work by Von Steuben concerning both Rifles and Dragoons. In he it does describe the use of a powder horn.
In the real world I would agree with you about loading them, but you sound as though you would wish to ban them. I hope I'm not reading this right. Sounds a little extreme. After all as far as I know most Rev-War Grenadiers still carried match cases but I doubt they were carrying a slow match in them.