In real pinball machines, aim assist is achieved through the use of magnets! Essentially, the ball is subtly boosted and course-corrected in select locations, but not to the point it's very noticeable. It definitely improves the game feel, though.
We ended up doing both in the alpha build that's currently up - we rearranged the existing ramps slightly so there's a clearer line of sight, and adding in some aim assistance (velocity of the ball is boosted when entering a ramp at the correct velocity). I think eventually it'd help to both overhaul the entire physics system (we used GMS2's default physics engine which I believe is based on Box2D because let's face it, coding slopes from the ground up during Ludum Dare is not a good time) and add more precise ways of controlling the ball in ways that aren't as noticeable to the player (like adding in "sweet spots" to the flippers that, under the right conditions, will always go to a particular area of the board). And of course, redesigning the board with much more thought put into the positioning of things in regards to the arcs of the ball will help!
P.S. Sorry for the belated reply! I want you to know we appreciated your comments :)