I've done "what 40K army every homestuck character would Play" but now I want to do what every homestuck character would actually be in 40K
Rose: Tzeentch corrupted heretical rogue psyker (easiest answer by dar)
Jade: Navigator (the noble mutant freaks w a monopoly on guiding Imperial ships through The Warp to allow FTL travel)
Dave: Least abused and unhappy space marine (White Scars?)
June: Aeldari harlequin because I think that's really funny
Vriska: Aeldari Corsair (easiest layup in history, space elf pirates who like to think of themselves as heroes)
Terezi: ordos xenos inquisitor of a more curious and investigative branch in order to facilitate 40K vrisrezi)
Kanaya: blood angel (space vampire bloodlusted berserker with a chainsaw) or Asuryani striking scorpion (often bloodlusted chainsaw wielding elves, green, can switch from path of the warrior to a caretaker path later)
Jake: rogue trader (space gentleman adventurer)
Jane: imperial noble involved with the Inquisition
Roxy: Unsure, maybe an Asuryani spiritseer?
Dirk: wayward Drukhari incubi (perfect swordsmen with emotional issues)
Feferi: T'au etherial ("benevolent" ruler caste)
Eridan: Ordos Xenos inquisitor (CEO of racism)
Gamzee: one of the more xenocidal harlequin troupes
Equius: Drukhari haemonculus (arrogant fetish driven space elf surgeons)