If you were making a mod would you require all the DLCs as esms so you could take advantage of their assets or just Skyrim itself so the most people can use them? I'm including a mage's garden so I'd like it to have a complete set of growing plants. Except maybe quest specific plants.

If you are really concerned, make two versions. Make it for Skyrim only at first, then add the DLC content you want to a second version.

However, I would think most people would have the DLCs that are playing the game now.

you can also use GetFormFromFile to check if a dlc is there without having to add a dependency.

usable for using assets only within limits though

i don't have any of them.

early buyer's curse.