Kingdom hearts 1+2 are my favorites games and will ever be. the story, the graphic, the animation, the music, the life in it, its so impressive.

yeah your style is cartoony a lot allready. if you really want to increase it, one thing might help. you should try to bright up your textures and objects, like 100% albedo or the other thing (forgot the name, i stoped gamedesign, so i forgot xD). ahh ambient.. was it? whatever. but this might help, it looks more cartoony then too.

and yeah shaders sucks xD i dont really like shaders. i love those shaders without any puixel or vertex version, cause they run almost everwhere. but im too much in love with bloom shader, heat hazard and cell shader. i love it. but i dont really use cell shader often, dont know why. the 3dgs shaders slows down the game a lot (i think it creates a copy of each model, give it a black texture, scall it and flip the normals) but i love the shadows on it, and i always use vector style for pictures so yeah thats why i love cell shading.

but really, keep your graphic style, and try to bright it up when you want it more cartoony, that might help.
anmd use point shadows