Batching sprite/billboard draw calls a la Instanced Static Mesh?

I’ve got these simple billboard sprites I want to iterate to act as a crowd in stadium bleachers. All of the “sprites” are Material Billboards using the same material, with the same size, so it should be possible to batch them into a single draw call, theoretically.

I can’t just flatten the individual audience-member sprites into larger chunks due to how billboards work (it’s okay if the sprites rotate “in their seats”, but for entire rows to rotate to face the camera would be really bizarre looking as they’d turn themselves out into the air). I COULD use Instanced Static Meshes to save on the draw calls, but I feel like trying to Tick each of these to keep it rotated toward the camera would negate the performance benefit of instancing entirely.

Is there some clever way of doing this? Or am I just stuck?