My apologies if this has been covered. I did a search, and failed to find something relevant.
I was very disappointed to find that Kruber’s face was always going to be covered as a Grail Knight, especially given the wonderful variety of helmets and hats he has in his other careers.
Is there a mod out there that allows (for example) his Mercenary or Foot Knight head cosmetics to be used with the Grail Knight? (And if not, would Fatshark consider enabling this? It can’t be a bad thing if people are willing to spend more money for a little cosmetic tweak, right?)
As mentioned by Slayerkin, the only head cosmetic where you can see his face is the Sharkhead which has been a time-limited cosmetic though. If you don’t have it then chances are low to get it now (unless it magically appears in the gift calendar).
This is a bit more complex. There do exist mods which allow to use the head cosmetics of other classes, even across different characters which leads to some very strange and unfun results. However, it is not sanctioned so you can only use it in the modded realm.
In addition, the head cosmetics and the heads are not separate entities. So if you use the FK no helmet cosmetic on Grail Knight it will look identical to the Foot Knight. This isn’t necessarily bad but take note that Grail Knight canonically is unbearded. This can be seens within the Shark Head cosmetic as well as the Engineer Release trailer (you can hit that one up on YouTube).