Make sure you set the game to only update on Launch, otherwise it will still download the update. This way the Workshop Connection remains. You can avoid the update by disconnecting the internet after you've logged in to Steam. This problem affects ALL steam games with a Workshop connection. Please be realistic, this is a multi-million dollar business, not a neighbourhood supermarket. That would cost them million of dollars for breaking the contract, invalidate every single copy of the game already sold (Including yours!) and force everyone to re-buy the game, and force the company to invest millions in setting up their own Workshop system, because using a copy of Steam's system is a patent and copyright infringement. They can't just break a contract and switch system.
(Unless they're EA we all know EA has no common sense.) I did move my game files from my regular harddrive to my new SSD (I redownloaded the whole game). When I try to download or subscribe to something in the workshop, it doesn't download anything. It does say that I am subscribed to them on the bottom Steam Workshop tab.
No company with more than half a gram of common sense would ever consider doing so. I'm trying to activate my mods for After Dark but none of them are showing up on the Mods Tab. That would mean dropping a market of 20 million users. Paradox is not going to 'drop cooperation with Steam and make their own workshop'.