I've figured out how to get my LOD for my Mountain meshes in a region I have generated with nearly 1,000 mountain meshes. So you see the importance of this to me. I'm not sure that this will work for architecture, but I'm fairly certain if you are having problems with Architecture LOD, this may help.
First off, if you're afraid of a slow and tedious work this isn't for you. I have a 1,000 mountains to do, and will be doing it.

Not only am I generating the Mountains, but they also presently include custom textured Mountain meshes that are side by side with vanilla mountains in the CK and in the game. Meaning I can have 5 mountaincliff01 models side by side in the game and all of them with different textures.

To get your different textured meshes, you need to know how to hex edit. I'm not going provide links, what to get. That's up to you, but I will show you how to do this.

Secondly, this may seem like a hard and long job to achieve this work, but with all the broken CK features and incomplete tools, well you decide if you want to use this route.

Creating the New Texture model:
After creating your model and you have your texture, rename it to what ever you want. The texture path though must follow the following rules.

The filepath of the model textures can not change. You can change the name of the texture but you can not change the length of the texture name.
So if the texture is called "RedLight.dds" you can change it to "GrnLight.dds" (the character length of the name did not change). If I had changed "RedLight.dds" to "GreenLight.dds" then the character length has changed. That will result in either no texture or reversion to the original model's texture.

Creating the LOD: I'm not going through the process of the TGATextures, you must know how to perform that before getting to this stage.
The Mountain LOD's as most of you know have differing LOD levels (0-3) from low quality to HD quality. In your render window, these statics (including architecture) have a flag ticked "respawns". Without any tests performed yet, I'm assuming it fascilitates the transitions of the LOD levels. In my opinion this is for game optimization? I'm not sure. My process with some testing resulted in ticking ONLY the object "Full LOD" on the object in the render window. The flags that are set for this is "Quest Item / Persistent reference, Random Anim Start / High Priority LOD, and NavMesh Generation - Ground" which you can verify for yourself in FO3Edit. These flags can be ticked either in FO3Edit or the CK render window for each object. the result is your LOD is essentially VWD's I think. Either way, this works for me and I have FULL LOD for my 1,000 mountains.

Due to the nature of MERP's masters, I'm able to use FO3Edit at full functionality. I know that nearly all others outside of MERP's mods, this won't be possible which means your solution will have to tick the flag "FULL LOD" within CK's render window for your object.

Update, actually this is not lod in the true sense of mesh optimizing. Its simply objects flagged for VWDs
and are not optimized for visual performance. However this process does work if you want more than one mountain texture.

1000 mountains at full LOD ? Won't this have a big hit on performance ?

Not really, testing shows that I have no issues, fps drops and I don't have a high performance pc. At a distance, its not an issue but up close where normal local textures are used there are none either. Partly because these mountains are anywhere from scale 1 to 2 and fill cells from 1-4 or more in numbers.
Still, this process allows multiple textured mountains, and until a system is released and working, this is working.

I need help for the minor meshes liek walls and stuff those get always messed up and switched textures , I can't affort to put full lod on all those meshes , I need to find a way to make lod work ...