I know this may sound a bit repetitive like the others but ever since this mod made by a mod team:
https://www.nexusmods.com/warhammer40000spacemarine2/mods/147

-Makes it possible that in depth customization is possible even with a mod team with limited access to the game files. so if the devs utilizes what they made (maybe even collab) using the full capabilities of the game files. Customization options for space marines would be absolutely crazy. I am a console individual so I can't enjoy a mod like this but if Focus Entertainment does something like this. It would be amazing.