Apect Ratio Transform and Grain Update

We need a tool to change the aspect ratio of a frame, for example, from 4:3 to 16:9 or 21:9, etc. It would be very useful when working with a direct file from 35mm film that needs stretching or with a 4:3 copy, so we don’t have to go through Premiere Pro or Media Encoder beforehand.
It would also be great to have more options regarding film grain, or even the ability to add externally scanned photochemical grain from a file and process it.
An anti-flicker filter would also be very useful.

An example Aspect Ratio Transform

El Dia de la Bestia - Frame 4 30