Motion blur without decay?

Duplicate layer isn’t that heavy on computation,

This example you provided is heavy for computation because it is using Duplicate layer which has Motion Blur layer below it. Motion Blur is very slow, I avoid using it.

@bjyitu has already kinda found out the solution, here’s a modified version which may solve, your (@pablogil ) query. bjyitu your example for onion skinning didn’t use Time Offset parameter, using TimeOffset parameter you can create true onion skining and not worry about linking individual parameters to duplicate index value, just delay the animations using Time Offset parameter by connecting it to the Duplicate Layer’s index value.
Some times things don’t work good with TimeOffset, Speed and Duplicate Layer (more)

onion.sifz (2.7 KB)
And your original
example.sifz (2.7 KB)

I think type of interpolation is important here, also the time delay between “subsamples” also makes a significant impact, I believe your effect and shown by bjyitu are same, just different implementation of same thing. How you animate the shapes is also important.