LOD For Large Complex Mesh (and Blender)

Hi all, I've done some pretty thorough digging and I can't see, to find any info on what I'm looking for. I'm really hoping that doesn't mean it isn't possible... so if anyone can provide me with any insight or at least point me in the right direction, it would be really appreciated!

I have a 3D model in blender from a client, not one that I designed, and I can't disclose many specifics due to an NDA. Ultimately, manually editing the blender model is not going to help out because this procedure should inevitably be applied to several models of similar composition. What I am trying to do is apply LOD groups to the sub meshes within the model, in order to improve performance of viewing this model in Unity.

I already have multiple variance in LOD for each sub mesh in the model, but when I import the model into Unity, it groups them all together- instead of within the distinct sub meshes. This kinda defeats the purpose because it renders the entire model in LOD0 when you come near in, when I want it to be that only the parts of the model closest to you are LOD0 and everything you aren't directly near get reduced.

I can't show the model in question due to the NDA, so I will try to provide an example using monkeys. Again, I need a procedure that can be applied to several models, so manually changing everything isn't the answer. However, to demonstrate what I'm looking for I manually developed an example.

The first image is what I want. Each part has its own LOD that calculate individually from the others. The second image is what I get now, where all of the parts are calculated as one LOD.

Currently, I am exporting the blender model as an FBX, but that isn't required if there is a better alternative to help with this.

If there is any setting or process or script that can be applied to either Blender or Unity that can give me some kind of progress to my desired results, please help! Kinda desperate because none of my plans counted on this being an issue, and I will have a major set back if this can't be resolved.