I'm sure this has been said before, but it would be great if the Mark 7 helmet could be added at some point, instead of being limited to just the Mark 10. A lot of us are used to it being the iconic Space Marine look in pretty much all of the Warhammer 40K material, especially in the video games, such as Dawn of War or Gladius, given how it has been around for years, if not decades (although I'm not entirely sure when it replaced the Mark 4).

Also, it would be neat if the Marines Malevolent chapter emblem could also be added.

id love mk6 more, a mk8 helomet is present in the trailer so it maybe in game, wouldnt say no to have a proper mk8 helmet

Mk7 is so iconic for so many fans I wouldn't be surprised if it turns up pretty soon - same for the Mk6 beaky.  So much to be excited about.  

Mk7 & 6 would be great. I can only assume they will be implemented with time, however you can create an idea on the idea section where you could suggest it.

For example here I did a thread for a Blood Ravens 20th anniversary skin dlc; https://community.focus-entmt.com/focus-entertainment/space-marine-2/ideas/372-blood-ravens-20th-anniversary-cosmetics?page=1

Mk. VII and MK. VI would be great. Although, I think they are canonically not compatible with Mk. X so we'll just have to see if they're gonna prioritise choice or lore.​