I love this idea but I couldn't "ride the beam" as they say. Keep working on this!
p.s. Consider adding another BoxCollider2D set as a trigger to your projectiles and setting up the OnTriggerEnter2D and OnTriggerExit2D callbacks on their script. In OnTriggerEnter2D, set the projectile's transform as the parent of your player transform. In OnTriggerExit2D you de-parent the player from the 'platform'. This will cause your player to move with the beam until they choose to jump or move off that collider. That should make it much easier to stand on the beams!