I'm not sure how profitable it would be, but one thing I would like to see is super high end gaming accessories. Things like high quality leather handheld system cases and high quality metal styluses for the 3DS XL (like the ones that used to come with $400 Palms and Pocket PCs, I hate the plastic ones.)
Also, controllers. Most controllers are made of plastic, some better than others. How about a luxury controller? Super comfortable, with the exterior being made of some kind of soft rubber or something to make it feel good and not just a hunk of plastic. Think of the difference between driving a BMW and an old Ford Escort. I got that idea from my car, actually. I updated the interior from vinyl to sexy leather, and noticed my shift knob isn't much larger than a Sanwa ball top, and I wondered how a soft leather joystick would feel.
Yes, I know all that would be expensive as f*ck, but hey, Hori released the VLX line of sticks, so they understand there is some small marked for super awesome high end stuff, but I am unsure if that actually brought the company any profit.
By the way, if you happen to know any of the guys who designed the 3DS XL screen protectors, tell them that they f*cking rock. It fit perfectly, the new weird way of applying to the bottom screen made it a snap to install, and it seems invisible once applied. Best screen protector ever.