I didnt understand a word this said
Lovely idea, however this only rectifies the problem for elemental ninjutsu.
What about ninjutsu that has no specific chakra nature? or fuuinjutsu? genjutsu? summonings? senjutsu? and forbidden jutsu?
I am aware that all of the above may have element related jutsu but I don't think that 25 or even 125 options is enough to cover all of the above.
If an individual is having trouble using one hand to move and cast jutsu then I would advise using two hands. With enough practice a 4 combo jutsu can be cast in less than a second which, even in this fast paced game isn't alot of time.
If that's still not satisfactory, I could advise you to do what I do; I hold my pinky on one of the WASD keys (keeping me moving in one direction) and use my other four fingers to type out jutsu. This isn't as fast as it could be but it is useful for casting while moving in battle.
I think I understood this and it's a cool idea though I'm not sure if this would change.
Reason being is that not all the same type of jutsu have the same starting handsigns (in naruto at least)