I got early access on Steam, when I first started the download it said there was 229gb to install due to all the addons I had so I decided to disable the addons which reduced it to a more manageable size, I did read somewhere when it came to installation of the addons you can just copy over the dlc folder from TSW 4, I found the file but not sure where to copy it to?
If you do that, you're not getting latest versions and you'll just have to have a big download whenever any patches come in. You may also experience unreliability / crashes due to this. Definitely don't recommend it. But, it may work, to a point. Matt.