Alright, I'm gonna share with you what I did-
Version C. What you'll need to do is make the collar longer, change the front to have no opening and add a seam, and extend the shirt to where you need it.
The back looks exactly the same as the front(Thank God for the anime opening- it shows the back of Aporro's outfit, and I was tearing my hair out over whether or not it was the same or not as Kubo neglected to show any shots of the back of Aporro before release)...
We'll leave the black detail out for now, as I need to explain the sleeves first.
IF you wanted to be perfectly seam accurate, you would need to merge the sleeves with the collar- meaning the collar and sleeve would be one piece. Impossible if you don't use fabric with stretch...and difficult even with. Kubo is an arse sometimes, though, and doesn't usually draw seams, so you can get away with a seam on the collar.
Extend the sleeves to down to the middle of your hand(not hard, just be careful), add the thumb hole and now you can start on the black.
You have two options- line it in black and the black details can be either zippers or
bias tape, or take the easy way out and leave it unlined with black bias tape as the detail and of course, have the black zipper in front.
Stretch fabric will cause the bais tape to waver and pucker, so what you need to do before sewing it all together is take the seams where the black is going to be(this includes seams where the zipper is going to be AND the thumbhole and end of the sleeve), and interface them with lightweight to mediumweight interfacing. This will prevent it from wavering and will make it easier to sew.
The stirrups from the Akatsuki are the same as Aporro's, so no difficulty there. I'm sure there are threads on it. (If not, measure around your leg WITH the boot on, take a rectangle of fabric matching those measurements[use the stretch fabric you used earlier- it will be easier to take on and off], put in a 5/8 seam with a zig-zag stitch, slip it over your boot and see how it fits. If it slips, make the seam tighter. If it doesn't, great.
Adding the little stirrup is easy- flip the cylinder you made inside out, measure across your foot between your heel and ball of your foot(meaning the across the middle of your foot), cut a smaller rectangle, hem it, attach it to the cylinder and zig-zag stitch it in place. Make sure your foot with the boot on can still fit inside. If not, seam rip it apart and try again.
Best of luck~!