This is mainly for intelligent lighting.
Have it so you can select a fixture(or group like in Editor). Place a "point to marker" and light(s) will aim to that point.
Add another marker (step) and lights will move it it. Just like Editor you have the ability to adjust the movement type and duration. (though if you need to port to Editor to adjust those settings I am fine with that.)
The 3D View is already a virtual grid.
It already has the ability to place an object anywhere in said grid.
All the lights have both a starting point and their mobility already per-defined. Shouldn't be to much more to implement this idea.
This would make programming SO MUCH better and faster.