What most PW owners do is combining lots of haks into one naming it something like MyPW_A and myPW_B and so on. That way players get those haks in fewer downloads, but I really hate this method because I've only tried three PWs so far and got over five GB of content that is mostly all the same just put into different haks. I don't mind having to download the same stuff again, that happens only once for the PW, but I'm stuck with gigabytes of content that I'd really only need ONCE. If the hak isn't changed there's no need to put it into a different hak and if just a few 2da files are changed, they can go into a top hak and the other hak can stay unchanged.
Why not putting all the needed haks into a zip (or 7z) file instead of a hak? That way if the player unpacks the files into the hak folder and has a newer version of tileset xyz he can choose not to have the older version override it. Only files he doesn't already have will be copied to the hak folder. I think I have all of Worm's tilesets at least thrice. Is that really neccessary?