I think a useful client side script feature would be the ability to cap draw distance.
Reason for this is whilst the user usually sets their draw distance as far as performance permits, inside skyboxes, it is often not desirable to render neighboring skyboxes, or one skybox casts a shadow over another etc.
If we had the ability to cap draw distance from client side script, a script could automatically cap draw distance when the user enters one of these skyboxes for better immersion