This is a very interesting idea, though it may become tricky when new versions of popular downloads are released. As the popular markings/item packs are updated, the links would have to be updated as well, which may become a bit hard to keep track of. In addition to this, it's possible that we would need permission from the owners of the marking/item packs in order to provide a link to them on the official website. As a few users above have mentioned, the users who download the markings/item packs would still need to know how to download those modifications, and while providing an "official" platform for them to download these from, I'm not sure how significant a difference it would make. There seem to be quite a few threads that come and go that discuss popular/favorite markings and item packs, not to mention various advertisements for these packs, and the more popular packs don't appear to be all that difficult for new users to find. Most of the popular markings/item packs that I've seen do include instructions of some sort, so unless a fluff is having a bit of trouble figuring out where or how things are supposed to be moved, they do a pretty fair job explaining this. Perhaps it's a bit of an unpopular opinion, but I also feel like it may look like we're picking and choosing which markings packs are better than others? Of course, I don't think this would be the case, but it may do well to take it into consideration, and advertising specifics might discourage users from downloading other ones.
Very cute idea, and I like how you're thinking, but this is only my opinion on this. I'm interested to see what everyone else thinks. <3