Huh. This is... actually, I rather like this idea. However. I don't see it as being very realistic in practice. Mostly because the collaboration on a project like this would be huge. Not to mention the fact that, with every update someone has to their own pack, it has to be updated on that list and then people would need to redownload this list and there may be requests all over the place for people to add/remove their items from said list and copyright issues and so on and so forth.
On the side note of the items being stored publicly on server, as some people have pitched the idea about all presets being able to be seen, that would use up a lot of storage, which would require a bigger server which would require a lot more money. This could mean needing to buy a membership, which was highly frowned upon when the official poll for that went out on presets.
Good concept, sketchy in practice. But I don't know, maybe we can in fact get things working...