I’d like to propose a general purpose onion skinning feature for animated objects/blender viewports.
What is known as ghosting in other 3D packages (I think 3ds max) is already part of Grease Pencil. This is extremely useful for animation, as You see arcs and spacing in screen space. Onion skins are equally useful for 2D and 3D animation, and a much better way to tweak and fine tune animation than fiddling with f-curves 
What do You think?
I’m sure it’s on the list for Animation 2020 (haven’t seen it on the roadmap though, but that module seems a bit patchy in terms of documentation)
There are some addons that do ghosting, haven’t tried them though just because I thought just by looking at the screenshot that it’d slow down my playback which isn’t fast as it is. (I know, it’s stupid to make such assumptions, I’ll give it a try one of those days)
I guess Animation 2020 is just what it sounds like
Yeah I have an addon for onion skins. It works, but slows things down a bit. Or a lot, but I haven’t found a reason other than it being in beta.
So I can hope for a cleaner, faster native solution then.