I'm working on my own design of an rpg, but I do not know if it would appeal to gamers. Please note that this is merely theoretical; I am still working on all the controls and will probably program it into my calculator first. Basically I want to make an RPG that uses only the number pad and mouse(or the q, w, e, a, s, d, z, x, c, and a few other keys if you are left-handed) I know that this is slightly different because usually controls are 4-directional with wasd, ijkl, the arrow keys, or 8456 for the directions. I'm worried about this part because controls are the main thing that matters in any game(would you play Pong if the right control made the board move up and up made it move down?). I'm probably going to work on it anyway, but it would be good to know if it is worth publishing.

Just allow the user to customize their own controls. The real question is, are you using too many buttons at once? If the answer is no then chances are people will easily adapt.

Don't go beyond forcing the user to press 3 buttons at once during gameplay. Most games never go beyond 2.

Would it make more sense to make the game controlled by a USB gamepad instead? Gamepads are made for 8-direction control.

Do you really need four extra buttons for (I'm assuming) diagonal movement? Why not just press up and left to move up-left?

I've played games where there was eight button movements on the numpad, and frankly I thought it was cumbersome. I find it much easier to hold down two buttons than it is to move my fingers around the keyboard for diagonals. At this point in my gaming career, I would find it counter-intuitive if I pressed two movement keys and didn't get moving in a combination of the directions indicated.

+1 on the customization route, also. Especially if you have a "jump" button; the jump button is never in the right place.