hi,

the passable parameters are limited to (as I know) TEXCOORD0-7, COLOR0-3 (not sure), and FOG (this depends on shader model used). maybe you could combine somehow the lights in the vertex shader into the 3 parameters you are passing.

a while ago I made a terrain multitex shader handling tile normalmaps (based on the shade-c terrain shader), but it was slow for my purposes. maybe I can add this feature to my current terrain shaders in future...