Hello Benjikan. This is not really feedback but more my personal observations. (which normally raise as many questions as they answer)
When shooting fashion where do you keep the aperture settings? I shoot with a Sony A-550 with the APS-C size sensor. I do not have any examples to post but for the most part it seems the 85mm F/1.4 yields a softer image than the 50mm F/1.4 (both Minolta Maxxum lenses)
I do understand that my shooting portraits is different than your fashion work as it seems that fashion photographers are not looking for the shorter depth of field. As an example I had a woman come it with straight Black hair that glows under the lights and shows fantastic detail. At F/1.4 the DOF seems so short that the detail is lost and her hair starts to get fuzzy where shooting at F/2.8 gave the hair more detail and maintained the shine and texture.
Many years past I took a class for pointers on how to use my Mamiya medium format film camera and the thought process back then was to keep the camera the same distance from the subject but use a 135mm for a single individual and something along the lines of an 80mm or a 60mm for couples and groups.
I like the 17-50mm F/2.8 when I am moving around and have started using the 50mm F/1.4 on the tripod. I put the 85mm F/1.4 back in its box and it now resides in the cabinet with everything else I do not use often.
What I think I am seeing would seem to fall into line with what you have said above I am just not sure how or if it would apply as I am trying to do portraits where you do fashion and the requirements seem to be different.