Interesting ideas. I agree though: Extensive work with fine details is needed for this to look right.
When building a large model it is tempting to have large flat areas. However when building larger models I always have a regular sized vehicle next to it. If the thing is to look right I want to hit about the same "texture density" on the large model. Ie. Having large areas without anything is a big nono in my book.
I remember seeing (I think it was in the BFG parts of the forum) someone scratch building a Star Wars Star destroyer. The model is actually a fairly good example: The basic shape is simple enough, but to give an impression of size the tiny detail becomes very important: The "techy" looking areas sandwhiched between the upper and lower sides of the model is an important feature to give a sense of size.
Although much smaller than what you have in mind, my CI conversion illustrates my point:
At first I just put the basic shape together from plasticard. It is a lot of work, but I tried to cover the entire model with textures and shapes that you would recognize from other Epic models. The gothic windows are the same size as the ruins spures, the infantry statues (obviously), and the spaced armor plating similar to lucius pattern titans. Looking at the model I still feel the treads are the most problematic part of the model since they still look oversized and are too easily recognizable as 40k bits.
Using 40k parts as a basis for Epic models is cool, but they require extensive camouflage IMO
The mobile mining platform sounds like a really cool project: Adding some model railroad refinery bits, or maybe an offshore drilling platform drill tower would be an interesting start.
