Hi Will, actually in v2 there is already something in place to make Grid snap automatically take precedence over "On" Object snap when both are enabled - it should kick in if you are snapping on to a line that is oriented parallel to one of the grid axis directions.

Here's an example - note how the "On" snaps on this line go in grid increments:




It's not really feasible to do this with just any regular curve though, because it would involve quite a lot of curve/curve intersection calculations.

- Michael