Just in case anybody else is trying to get BTML & ModTek working on macOS, you can do so using a Windows machine to run the BattleTechModLoaderInjector.exe and modify the Assembly-CSharp.dll
I suspect it might need to be done after every update though...
Here is how I made it work on macOS, using a Windows machine to modify Assembly-CSharp.dll
For thos unfamiliar with macoS ~ is your user home directory and Library is a hidden directory inside it.
Copy ~/Library/Application Support/Steam/steamapps/common/BATTLETECH/BattleTech.app/Contents/Resources/Data/Managed to a FAT32 USB (you have to take the whole folder)
Place BTML files in the new Managed folder.
On a Windows machine navigate to the folder in the command line and run the BattleTechModLoaderInjector.exe
Copy modified Assembly-CSharp.dll 0Harmony.dll and BattleTechModLoader.dll back into the original installation under macOS.
To add ModTek support
Create ~/Library/Application Support/Steam/steamapps/common/BATTLETECH/BattleTech.app/Contents/Resources/Mods
Copy ModTek.dll into this Mods directory.
This is also where you put any ModTek compatible mods you want to run.
I suspect it might need to be done after every update though...
Here is how I made it work on macOS, using a Windows machine to modify Assembly-CSharp.dll
For thos unfamiliar with macoS ~ is your user home directory and Library is a hidden directory inside it.
Copy ~/Library/Application Support/Steam/steamapps/common/BATTLETECH/BattleTech.app/Contents/Resources/Data/Managed to a FAT32 USB (you have to take the whole folder)
Place BTML files in the new Managed folder.
On a Windows machine navigate to the folder in the command line and run the BattleTechModLoaderInjector.exe
Copy modified Assembly-CSharp.dll 0Harmony.dll and BattleTechModLoader.dll back into the original installation under macOS.
To add ModTek support
Create ~/Library/Application Support/Steam/steamapps/common/BATTLETECH/BattleTech.app/Contents/Resources/Mods
Copy ModTek.dll into this Mods directory.
This is also where you put any ModTek compatible mods you want to run.