Essentially, this would be a small addition to the way collision works with contraptions: the movement of the contraption would add to player speed for a short amount of time, with the player carrying their momentum while in the air/jumping. This would add some nuance to parkour maps.

Essentially you can build your own weighted ejector, and get ejected out of your trajectory by another custom ejector.

Interesting idea, reminds me of Celeste's mechanics