[FEATURE REQUEST] Make an animation with the ViewBox changing dynamically

[giacomomarchioro]

Is your feature request related to a problem? Please describe.
I have an animation with a "zoom like" effect where I change the view box so that I can zoom to a detail.

               <animate
   attributeName="viewBox"
   from="0 0 1080 1350"
   to="323 167 523 300"
   dur="5s"
   begin="0s"
   fill="freeze" />

Unfortunately when I export the video, setting the view port manually:

timecut manuscript2.svg --viewport="1080,1350" --fps=30 --duration=5 --frame-cache --pix-fmt=yuv420p --output=video2.mp4

the "zoom like" effect is lost.

Describe the solution you'd like
I would like to be able to export the animation with a defined aspect ratio e.g. --viewport="1080,1350" and keep the "zoom-like" effect.

Describe alternatives you've considered
An alternative would be to keep the viewBox fixed and apply transformations to the all the objects.