A standard feature in a lot of mobile VN's is tying a slight amount of background movement to the current speaker, to add a little dynamism to back and forth dialogue. You can see an example from an app I worked on here:
https://youtu.be/vjNsB62HEOc?list=PLYF_ ... vLM&t=1688
The way this is handled behind the scenes on that particular app is, one character is designated as the main character and everyone else is an NPC. The main character displays on the left side of the screen, and all NPC's are positioned on the right. If the main character says a line, the screen shifts left. If an NPC says a line, the screen shifts right. All other text doesn't affect the screen position.
Right now it's possible to do this in the Naninovel engine, but you'd have to do it manually for every shift, either with poses or by setting the background's pos parameters.
I'd really like an API command that tells the engine, "Here is background XYZ position 1, which you should bind to characters Bob, Jim, and John. Here is XYZ position 2, which you should bind to characters Sally, Jane, and Ronda. When a character bound to a background position delivers a line, move to that position before displaying the line."
It's just a small game-feel feature, but I think it goes a long way toward making a scene feel less static. Particularly on narrow screens like a phone.