Champs like sion/poppy are so radical of a change that they would not benefit from a traditional really unless you kinda force it, but champs like WW are so similar to his original design that they should honestly give him a traditional skin
I'd actually argue that out of the 3 you mentioned,Sion is the only one who could really use a traditional skin.
And thats exactly because new Sion looks so different.
You see,a traditional skin is basically a skin for the updated champ that resembles his old design.It doesn't represent the old design to 100% and that would likely mean that traditional poppy would still look happy(otherwise they'd had to change her facial animations) and that traditional warwick would still have a machine looking out of his back. Traditional Poppy would be essentially a slight recolor with small changes to her armor,wheras traditional warwick would be the new classic warwick with gold armor at his arms,red eyes and smaller ears,so all in all,these 2 skins would be below 750Rp-skin quality.
Traditional sion on the other hand could easily function as a 750-skin(or even higher if he had his own lines) on its own and thus would make sense. I mean just look at this concept art made by a fan: http://a.disquscdn.com/uploads/mediaembed/images/1336/9960/original.jpg Replace the shoulder armor with old sions skulls(they'd be ok for china,since they are nonhuman) and maybe change his pants and you'd be fine.
Yeah that would be a cool skin. That he have his old red and gold armor things.
