Arma 3 Launcher preset functionality does support saving and loading of optional DLCs, it also exports info about them to the HTML file but that data seems to be not imported back into the launcher when the preset HTML file is imported.
This functionality is really important for groups that use Steam Workshop and provide their players with Arma mods preset files to load the mods. Seeing that most of the functionality seems to be finished (only the import does not work) it would be really great to see it finished.