Not sure if this is a feature in the editor you use, but in the editor I use, I can set an entire track to move from one point to another, and I can replace whatever image I'm moving with another image seamlessly and it'll just continue moving right from where the first image was.
So the way I'd do something like that would be to have multiple images ready with various expressions (all expressions in one image, so like... one image with four or so expressions) - I'd maybe do 3 or 4 "sets" with each set having a different array of expressions (or maybe just the same expressions but swapped positions, depends on how much you or the artist wants to draw) and just keep recycling them for however long the duration is, and set the track to start from point A and go to point B. And while it's moving, I'll just replace the image with the other images in the cycle one by one and that'd be about how you do that.
I'm not sure if there's an easier way to do it, but that's the first thing that came to mind, haha.