Feature request: more option to Onion skin module

[pgilfernandez]

Is your feature request related to a problem? Please describe.
I used this feature a little bit and I miss some features that I would like to describe:

Describe the solution you'd like

• option to add a tint color for past and future frames/keyframes. This way it would be easy to distinguish between past, future and actual frame

• as you see in the previous picture, the actual frame stays on top so that you can easily work with it

• option to "skip some frames", I mean, if you are using onion skinning frames (no keyframes) it is very probable that your past/future frames reach the maximum which is 10 frames. If the animation changes so little overtime you won't have a real preview of how the animation is in the past/future. I would like to propose a "step" option that lets you play with those 10 frames maximum but in the time... summing it up, something similar to the motion blur layer where you have the option to set the steps (subsamples) and the time (aperture). Some examples:
  

Describe alternatives you've considered
I don't know if these values may be added to the toolbar, inside a "onion skin popup", or inside Preferences

Additional comments
Thanks!

[KartikWatts]

Hi @BobSynfig @ice0, this is an amazing feature, I would really love to work on it, if possible to assign me.
May already start working on it based on the well-defined information provided. And can iterate on the draft based on the decisions required and preferences we would opt for the UI. Regards.