1. Binary alternatives to some commands, taking a camera as the LHS arg:

worldToScreen:

cam worldToScreen posAGL (or posASL, which I prefer)

screenToWorld:

cam screenToWorld uiPos (returns AGL, or better, ASL)

positionCameraToWorld:

cam positionCameraToWorld relPos (returns AGL, or better, ASL)

2. A new scripting command: screenToWorldVector, (alt names: posScreenToDirection, screenToDirection).

It's similar to the first step of screenToWorld, i.e. it returns the direction vector that is needed for screenToWorld to do the intersection.
The reason I ask for this command is that screenToWorld tries to perform an intersection, which is both costly, and may return undesired result.

Unary version for the main camera:

posScreenToDirection uiPos

Binary version for any camera:

cam posScreenToDirection uiPos