Could you make it so custom ghosts can show whats happened previously?

When i animate i like to playback the animation constantly so i can keep track of the bigger picture. Onion skin also shows previous frames which helps me keep track of how it looks and whats going on.

When I'm trying to make a replay in toribash i find myself constantly pressing R to see how the replay looks and what the motion looks like. It helps me see the flow and keep track of the momentum i feel like. It'd really help me keep track of motions if the ghost showed this info instead. So like turning on onion skin in an animation program so you can see previous and next frames.

Maybe this could be implemented by including an additional slider that goes into the negatives. and the ghost appears that many frames before and continues until it reaches the limit set by the positive slider.