Do you miss the feel of playing your Virtual Console games as if you were using the old NES Advantage? If so, the Cyber Arcade Stick by Cyber Gadget is exactly what you are looking for. The accessory, which is scheduled to launch in Japan this October for about $30, will transform your 3DS into an arcade / fighting stick complete with a balltop joystick.
The stick itself could be beneficial for fighting games although there aren’t many on the platform. However, the button sizes don’t change any so usage could feel a bit awkward. I can’t imagine being able to use this without setting your 3DS on a flat surface, which would then make the face buttons hard to access considering their size. So is it practical? Probably not. Is it still incredibly cool looking? Definitely.