A cylinder check between 2 objects and the cursor isn't hard to implement (check distance between a segment and a point smaller than radius of cylinder).
But does it actually "improve aim"? For reference, a lot of patterns can be played by keeping momentum and not snapping each and every circles, thus leaving the "line" by having a larger curve. This mod would therefore encourage new players to learn this specific playstyle instead of leaving it open to experiencing to find the best personal playstyle.
Edit: Additionnaly, some patterns are just meant to be played as a circle and not as individual lines