Same Objects Shared Material each with a different offset

Hi

I currently use a model in my scene which i want to apply different skins too e.g. Same Tree with different looks.

At the moment i have 1 low poly models repeated 10 times in my scen (all the same object) so i get 1 draw call.

To get each tree to have a different material i had to add a new material per object and select a new texture. So now i have 11 draw calls.

I want to get this to be 2 draw calls, so i tried by combining all of the textures into one material. This worked fine but of course the models all point to the same part of the texture which i unwrapped. No good.

So after this i thought for the other 9 trees, i could just set a material offset to point to a new part of the texture but i found that it changes it for all 10 object. i understand why this happens now.

I also experimented with trying another idea, i took my 1 imported model and copied it to make 10 models, then i unwrapped each model in Blender to use a different part of the same texture. Then imported them into Unity and when i add them into the scene i get 2 draw calls, not sure why this works, all of the models are identical other than a different name. I guess unity is batching them, but this is not great as the models just increase the Tris etc.

Any advice or help would be great! there must be a way to do this similar to how sprite atlases work.

Nick