I'd like to contribute my 5 cents to this discussion, without hijacking your thread Lady Nerevar. But I think my points are universal to some of the discussions I've seen here lately.
The reasons why large mods never or rarely see the light of day or get abandoned has already been discussed and is not the reason I'm posting. I'd just like to touch down on a few points and share some of my experiences while working on Sands of Destiny.
Actually, Sands of Destiny is one of those larger scale mods that is currently under a very similar struggle than Hammerfell, just in different areas, namely quest making as opposed to modelling. I've spent almost 2 years modelling unique and new assets for SoD and making the worldspace, which is now finished. That is only half the battle won though.
Perhaps I should've joined up with the Hammerfell team a long time ago. I could almost guarantee that Hammerfell would be much more progressed as it is already. On a side note, I must say that the quality of what I've seen from Hammerfell is absolute top notch. The reason I started Sands of Destiny was mainly freedom to do whatever I want without restrictions though.
But this comes at a price. Not only is it much more work, it will naturally be seen with much more skepsis from the community. Especially if it starts out as a one man band without a team. The skepsis part from the community is one of the reasons why I've never started an official thread on the forums. Too often people propose ideas (that sound great), but they have no idea what they're getting themselves in to (aside from the lack of skills). However, without continuous and active discussions, a project can't and will not progress. It will certainly not attract willing modders to help either. Therefore, things are much slower, ultimately leading to a possible abandoning of the mod. From my experience, It's not so much the lack of skills that stop a mod dead in it's tracks, but in my case all those "small" things that keep adding and adding and adding up. You just don't realize how many things need to be done when creating a custom worldspace. Especially if you're modelling custom assets at the same time and writing your own lore. Piecing everything together so it makes sense is another issue. That being said, I've always been willing to do the entire mod myself and have not yet run into any dealbreakers. The learning experience has just been tremendous.
As for modder's resources, I've tried to stay away from them as much as possible for exactly those reasons that Lady Nerevar adressed above. Eventually every other mod will start to look the same. Although the beta version of my Desert Architecture has been used in many other mods, the final versions as seen in SoD are very different and much more optimized.
Sorry for rambling on and on, but I just thought I'd share a few points.
~DE