Mouse/keyboard option in the game menu is not a bad idea but I believe that, in this case, both versions should have the same HUD-movement-circle design. The only visual difference could be that keyboard mode would be without the knob & mouse mode would be with the knob. Here is the quick sketch:



The problem is that in the mouse mode right-button solves the spell switch & consumption in one quick swoop, while in keyboard mode this will be very difficult: buttonX (holding) for potions to appear, buttonY to switch through & buttonZ to use? Or we could have buttonX (holding) for potions to appear, buttonY to switch through & when buttonX is released the potion is used or action is canceled if you switch to cancel slot (if switch player is South, cancel could be placed on North)?