Maybe a size adjust option, but by and large I think this is a bad idea. Most of the concerns you listed fall under the general heading of "make sure cosmetics are as uniform between 'frames as possible", which I absolutely agree with, while others, like trying to make your syandana look like a tail, etc. would a) be a ton of work for DE, b) open itself up to a ton of abuse (I still see melee weapons turned to come out of the crotch or floating free after they added holster customisations), and c) interfere with an area that DE has wisely chosen to leave as bare as possible: the base of the spine. That's where Titania's wings come from, as well as archwings, but it also features other Warframe-specific visuals like Volt's amp-generating external lump on his lumbar, Trinity's "lobster tail", Protea's belt/turret growths, and more.