Here's a fun idea.
How about in ESB when they are in the carbonite chamber. Chewie begins to fight with 3P0 on his back. How about we cut in a quick close up of Vader's face, and cut to a slow mo close up of 3P0. Then cut back to the next shot of Boba Fett preparing to shoot. But make it slow motion and cut in a slowed down version of NOOOOOOOOO.
Clearly the scene is about Vader wanting to save the droid he built from being shot by Boba Fett, but this way it will be more obvious.