An overhaul to the player pack structure is in the works to allow for different expressions, I actually posted about that on my dev twitter recently: https://x.com/YeahMaybeDev/status/1813055565133705537
As for animation, I would've done so already if it had support, but unfortunately the Godot Engine has no native support for animated image formats, so if I do manage something, it will have to be a work-around.