[Nisgeis]

The search light pixel shader appears to only affect the shading of the search light beam, the light spill cast on the surface is probably drawn in the engine and passed to the water surface shader, so probably not something that can be modded that way. The light spill effect will disappear when the light beam object is off screen, so I would theorise that lengthening the beam object and adjusting the alpha channel of raza2.dds would allow the beam to be on screen, but invisible and allow the spill effect to be drawn as well.