Just back up the game exe before it can be downloaded so you can use the older version until a new trainer can be made.
The changes this time is pretty minor, save games are now backed up automatically and if they can't be read locally they'll be re-acquired via Steam cloud sync if you have that enabled.
EDIT: Exe from 1.04
[Edited by LordJB, 9/8/2015 5:48:07 AM]
Just noticed that myself. The customization options probably have their own checks. Here's to hoping they unlock sometime later, maybe when you reach the requirements you were SUPPOSED to have when you do the research? If not, I'm a bit bummed out, but it is my fault for not backing up my saves before I tried out this option.
EDIT: Hmm, some of the handguns I unlocked seem to be customizable, but nothing else.
[Edited by SoM, 9/8/2015 6:45:07 AM]
The problem with it regardless is that any update, no matter how big or small, will change (some of) the memory locations so the CH devs have to redo pretty much everything.
Backing up your file and playing an older version can in a lot of cases be a violation of ToS when playing multiplayer (if it doesn't lock you out anyway), so beware of that.
Then it's a good thing multiplayer won't be available for PC before next year.
Am I right?
[Edited by Raizo, 9/8/2015 7:27:19 AM]
Never mind, my downloader managed it. Works. Thanks a lot.