I've been slacking off lately, I've nearly finished the shin piece I started a while back, but haven't yet (I started it with the logic that it was sizable, had some curves, had some tight folds, and I could **** it up a little bit without it being the end of the world). In hindsight, the shin piece is probably the hardest part of the entire build. The front half has all these little valleys, the back has all these little step height changes, and the entire damn thing is supposed to be curved. Nothing else has this demonic combination of size and complexity.
You've already heard of my first advice: visually break the part into some managable chunks, color code them in pepakura, and then cut and assemble those sections (I printed them out, and then manually abbreviated the colors on the individual parts, then printed out a couple isometric views with the same labels, it's been priceless in helping me keep everything straight, especially since I'm working out in the garage with no laptop). I did that after I had already printed the part out, the second one I'll probably rearrange the parts so the different colored sections are all together and I don't have to go hunting. This is as much for efficiency as morale, as I tend to judge how "close" I am to finished by how many pages I've cut out.
I'd also see about merging some parts together (particularly to avoid any really thin bridges or pointlessly small parts, because I've torn pieces while trying to cut or score tabs) and seperating some (some parts have these random slits running halfway through them to facilitate the entire part bending a certain way, which I'd like to avoid where reasonable). In case you didn't pick up on it, if you need two of a part, print and assemble one, then the other, so you can make these improvements. The fact that I have to do a second shin at all kills me.
Anyway, Hayabusa is definitely interesting, and I think you're a special sort of ambitious to consider pepping one. I for one was never a huge fan of the armor set (I'll invoke rule of cool as quickly as the next guy, but I specifically like the sleek military-practical look). I did sorta like the look of the shoulder pieces, and I wore one back in the Halo 3 days (come to think of it, if I ever get around to making a MJOLNIR set, I might make a Rogue helmet, more my style than EOD, and more practical than JFO or any of the other ones I like for the theme I want), but those are complicated so I'd understand if you opted against those. Come to think of it, I'm not sure how the Hayabusa chest differed from the regular one...
...good god man, are you going to build the katana? Please tell me you're building the katana.
And on a closing note, I recommend you try your hand at the undersuit. I don't really know how you would go about it, but it's one of those details that brings the whole suit together.