I'd probably handle something like this via nesting.
Make a 16:9 timeline.
Add 4:3 pic but don't change sequence settings to match it.
Now scale the image up in the timeline and introduce the movement you'd want that image to have.
now use that sequence as a clip on v2 or higher in your main sequence.
on you main sequence you can scale that clip down and give it whatever animation you want.
so now yu will have 16:9, with primary layer animation and secondary animation within the clip itself.
do that for each image.
hope that helps..
Alex Udell
Editing, Motion Graphics, and Visual FX
Let's Connect on Linkedin
Examples: Retail Automotive Motion Graphics Spots
Example: Customer Facing Explainer Video
Example: Infotainment & Package editorial 
