[Alteration/No Pattern] Altering a half-zip full-length Sewing Machines Parts and Sales in Los Angeles

Hi, first post (I read the wiki, very helpful so far!). This is a cosplay question, but since it’s regarding technique I thought it might do better here.

I’d like a bit of input on how to nicely alter an existing polyester cadet-collar sweatshirt into one shaped akin to a jacket for a Misato Katsuragi cosplay.

Though I figure I will be of course removing/replacing the zipper and continuing the existing twin-stitch seam along that line, would love some advice about how to do so while maintaining crisp look akin to the original. I don’t really mind if the zipper stays centered, even though the jacket’s depicted design calls for slight off-center/moto-jacket zipper placement.

I have a new decent machine and have the sweatshirt in a larger size, so there is material to spare if need be (plan to do side/length/sleeve alterations as per some online tutorials).

Many thanks!

Additional note:
I know sweatshirt materials aren’t ideal for this sort of jacket and to truly capture the jacket I should have made my own from scratch, but… as it’s my first real project I wanted to work from a basic garment.
I don’t mind if it doesn’t look “leather jacket” weight/appearance too much, but I will be trying to add a facing to the collar to at least make that character-accurate. If anyone has advice on doing so with this kind of fabric, or with nicely cropping/shaping the hem (akin to this cosplayer’s work), I’d also be much obliged!