Here's something I did while, admittedly, goofing around.
All these rumors of Z-forms for sun and moon got me to think about ash-greninja; the idea of your bond with your special pokemon (disregarding the more generic mega evolution) making them visibly stronger is very compelling (and also disregarding the obvious cop-out of "it only happened once before, ever" and that it happened with some random greninja and not pikachu); I still hold that it will likely not happen in the games due to the logistics involved, but it is very interesting in the "pokemon world" perspective.
So then, I got to think "how would be
my synchro-evolution pokemon?"; it's a good exercise, because it makes you think about what defines you and can be incorporated on a pokemon, and also on the pokemon, on how you can modify it just very slightly to match some amount of that, and I came up with these:
It wasn't easy; ash-greninja, for example, seems to have:
1- a change on the chest's color distribution to match ash's
2-a giant water shuriken on its back
3-a color-changed crest
4-beard-like formations on its cheeks, resembling ash's hair.
It doesn't take much to see that that's
very little to work with, when applied to other pokemon. It seems to be mostly about changing colors around and adding just something little; very hard to do, and I feel I went overboard with gardevoir, and I didn't do enough with ninetales, but anyway, I'm sure that so few things changed in greninja because it was only meant to be a one-time thing, so they didn't need to have many pokemon redesigned to match their trainers.
Both were hard to do, because I find them so perfect, there was little I could do to "improve" them; ninetales in particular gave me very little to work with, something I had seen already when I drew her for her card.
I should point out, before anyone points to my avatar, that I love capes, I always have, since I was very little. So naturally, they were the first thing I thought to add as greninja's shuriken replacement. Sadly, I couldn't find a way to add a tiara-like thing to ninetales; I feel that "just" cape+tiara are a good enough heuristic to apply to any pokemon I could possibly want to design as a synchro evolution (which in the end, seems the solution to the logistics issue; to think it around a fixed set of changes that are about
you, rather than simply what you're wearing or how you have your hair, since you can potentially change that).