That is why these differences should be added to their default form like many Ork fans have wanted. Not through their purchasable customization. Obviously the colour changes are one part but what about other things that should be like Goffs being slightly bigger, Bad Moons having gold teef, Evil Sunz moving slightly faster! Metal Glyphs and war banners are another thing.
I thinks it is an irony thing. It just looks so out of place that it starts to look right. Kinda like movies that are so bad they are good.
Kromlech has a superb range of minis with this exact theme, and it's propa flash! Even though the Nazi political regime in WW2 Germany was strict (if you didn't join, they made your life hell...sounds familiar to this genre) the German military made history during the onset of the war with the Blitzkrieg: fast-moving hordes of troops that overwhelmed their enemies (also sounds familiar, and with a really Orky-sounding name to boot!). So I think the style fits very well indeed. Although, I am of the opinion that this should be kept mostly (but not entirely) to Blood Axes since they are famous for swiping/imitating human military garb. I'm ok with this being among their sub-faction exclusive aesthetics, which every sub-faction will have (I think). (also, Kromlech is based in Poland, so if they're ok with making German army-style toys, I don't think anyone needs to be offended)
I wouldn't mind if it was limited to a sub-faction but I would rather it be accessible to other sub-factions even if it meant a greater cost to those sub-factions.