Yandere is more of a personalitty trait, not aestethic. Joker could be a geisha and a ganguro and still be Yandere.
I personally would rather go for frilly gothic-clown-lolita style or the ganguro one, the last one is funnier in my opinion.
But keep in mind, these are aestethic choices and doesn't say much about how the character should act, I think that it is important to keep the core of the character changed.
3 Jokers would be too much and weird in a random fanfic right on the beggining, but maybe it could be fun later. Lets be honest, we doesn't even know what the hell is going on with the 3 Jokers on the comic.