I myself own the DLC and am trying to passively persuade others to buy it, by using Global Mobilization assets in enemies and audio, et cetera.
I am trying to test the gameplay limitations of users who are loading the "GM Compatibility Data".
However I am not able to trigger the watermark in the editor preview (also when using a multiplayer server), nor seat limitation in vehicles. In this case I have the DLC disabled and the compatibility mod enabled. I was told on the GM Discord that the game engine checks for the presence of DLC, even when they are not loaded, thus removing restrictions.

This means that I am unable to create an environment that simulates GM compatibility data mod status.

I make missions for a fairly large group of players. The combination of requiring a 38GB download, and the uncertainty of gameplay restrictions, places the threshold too high for my group. This means that I will not risk using the compatibility data, almost certainly leading to missed sales of the DLC, since most players never experience the quality jump between free-tier "CUP" assets and the DLC. This is a feature request that I have seen before on the Discord, and I hereby request it myself.

Thank you for reading all this.