im so glad ive found this thread, i love all things diy, specially balmain from last three seasons ive been wanting to diy their whole collections. Right now i have my eye on the denim jacket you posted earlier, the studded cross jeans and the turquoise mini dress with the criss cross embellishments, but that one ill put on hold until i get my new dressform.
I havent met a good tailor or seamstress to recreate things straight off the runway, before i knew how to sew i also wanted the look for less but never found someone that could do it the right way.
The tricky part with the denim jacket is the sleeve- shoulder part, the way the shoulder sort of points up and out cant be done just with a shoulder pad, thats why the seam is not right at the edge but a little past the shoulder bone and has a squared shape, this allows the shoulder pad to have more room to stick out more. Also you will need to customize your shoulder pad, they wont be like that on the store. thats just trial and error until you find the right shape, just cuttin and shaping you store bought shoulder pads, maybe even using bra cups instead of shoulder pads.
Note also that the balmain jackets are meant to be worn open, and if you want to customize an already made double breasted jacket it wont look the same when open, since they always have a double layer for buttoning, the ones from balmain dont.