Yes, players need to be careful because small jumps are heavy, and big jumps are light.
Jump energy changes over 0.5 seconds, from small and heavy (tap), to big and light (hold). Careful timing is needed to get medium jumps.
I want the effect to feel like jumping is heavy, but if a player jumps with enough energy for a big jump they break through gravity, like they are in low gravity.
Yes, it is unusual, and it might be hard to get used to.
I think it's an interesting effect. Different. Not realistic. Like jumping in a dream :)