Why dont you put a laser inside the pen and use a mouse matt and make it a good laser etc and then just adjust dpi on it so its almost like the area of a tablet that you like. Its just an idea tell me what you think?
Normally when you use a tablet to play Osu you hover the pen over the tablet and you dont drag it. With the laser inside of the pen you would need to drag the flat and large surface area across the rough mouse mat or any other fat surface. If you really want to try it for yourself more power to you.