You seem to be concerned over your draw calls. Are you sure that the mapping is the cause of your draw calls? Do you have separate objects with separate materials? How many lights and what lighting mode are you using? Are you doing anything fancy with your camera renders? What kind of shaders and effects are you using? There are too many things that can up your draw calls. Please see this Unite presentation for some useful information.
Assuming that your materials are the issue, the real problem is that 3DS max materials are separate materials and even the blend/composite/Multi-SubObject materials only take in multiple separate materials, not separate maps.
If the only thing different about your materials is a map of some kind, then you can merge them into one map and apply them as one material, but if the material properties are actually different, then it becomes harder and you would either need separate draw calls or to generate merged maps of the material settings as well but that still may not reduce your draw calls.
Merging your maps
If your maps are blended in a fairly straightforward manner, you could author a simple 3 Blend shader in Unity that takes in 3 materials to do your blending and it would look kind of like this:
Shader "Example/3 Alpha Blended Textures" {
Properties {
_MainTex ("Base (RGB)", 2D) = "white" {}
_BlendTex ("Alpha Blended (RGBA)", 2D) = "white" {}
_BlendTex2 ("Alpha Blended (RGBA) 2", 2D) = "white" {}
}
SubShader {
Pass {
// Apply base texture
SetTexture [_MainTex] {
combine texture
}
// Blend in the alpha texture using the lerp operator
SetTexture [_BlendTex] {
combine texture lerp (texture) previous
}
// Blend in the alpha texture using the lerp operator
SetTexture [_BlendTex2] {
combine texture lerp (texture) previous
}
}
}
}
To reduce the memory and load though, it would be better if you just took the maps and merged them into one. You could use your image editor of choice, applying the appropriate deformation according to your UV's (which you can get with Unwrap UVW's if you need - look up UV unwrapping), or you could just bake the textures in 3DS max - RenderToTexture and add as output the map you want (diffuse for example)(see this tutorial if you're having trouble).
To make your life easier, with your shiny new merged map, in max, change the material on your object to one that applies your map. When you import into Unity, it should import only the one material with only the one map.
Separate material settings
You would generate one or more maps like the above for your material settings and then you would have to author a slightly more complex shader that applies the settings with the values you've input. Since I don't know the specifics of your materials, I can only guess at what settings would be different, but you could just look at the source for the built-in shaders for reference and adjust those.