A Way of implementing Hard Rock and Hidden

[HeyItsJinx]

Wondered if thats at all possible, i have a few ideas in mind:

Hard Rock:

smaller note hitbox meaning you have to be much more accurate aswell as less hearts to give you more health and more health lost per miss lets say like 1.5x more health lost upon a miss.

Hidden:

Notes disappear before they get to the hitbox kinda like mania except rush. maybe have them disappear when they are about a quarter distance away from hitbox.

[swoolcock]

My initial goal with Rush! was to make mods represented by a custom avatar, or perhaps special weapons or armour on the avatar. Ultimately it would just be a visual representation of the mods you have selected rather than "always use Devil Maria".
Things like Hard Rock and Hidden would just be a bonus ability or effect that the avatar has.