The deal is that I want to finish the Dawnguard before embarking to Solstheim, so naturally I don't want to be sent there prematurely via radiant quests. To prevent this can I disable the Dragonborn file at launch, or do I need to do so with a fresh, new game?

continuing with a Current save after disabling a DLC or Mod can be problematic. especially when you current have a Quest or Gear that was added by the DLC/Mod, and even more so if Scripts added are currently affecting anything in the world.

If you plan to do that, I suggest you start with a fresh save.. or if you really want to use your current save, just keep a backup in case issues arise.


Oddly enough, Morrowind and Oblivion seemed much more forgiving in this regard then Skyrim/FO3/FO:NV