Daniel, VERY interesting!! I think you've got a good idea of the concept that Colin and I spoke of. Breeches and waistcoat are done well. Based on what I'm seeing, I might try one more light shade on the tops of the folds, , but it depends on how you see it.
Using sepia on the coat is an interesting move. I see your coats generally as a warm, cream-type shade, as opposed, say, to the cooler, greyish pants and small clothes. I tend to see sepia as a greenish tint (I'm told by my eye doctor that I don't see the grey-green range "correctly", so keep that in mind), which is a little at odds with the warm tones of your coats. But I love that you experimented, and now have a great example of how much detail can be brought out on these figures. I like the treatment of the hat - I'll be asking YOU for tips on that!
Your question/comment about black primer impacting the colors put on top of it - I hadn't really thought about that before.
I don't want my colors to be "vibrant". Dulling them down a bit is ok with me. These were natural fiber clothes colored with food and plant dyes, from what I've read. They were worn in all types of weather, for a full season of campaigning. I'm guessing they looked worn out by the fall.
Because I intend for there to be several layers/shades of paint, my first coat of paint, after the priming, is more paint than water - 60-40 maybe, even 70-30 - so no part of the black undercoat shows thru unless I want it to do so. Subsequent layers are thinned more, with most of the water bled away by pressing the brush against the edge of a paper towel, before applying it to the figure.
I know, I should know better... I wasn't thinking 
