Hmm, aethetics-wise, the hood would be most suitable for the Psyker. 

Yes, this game could use some love in this department. A hood is a nice choice, though it would need to be a bit different than the one used by the Tech Adept. Another one I'm missing is the typical inquisitorial tall hat (as seen in the Dawn of War II Retribution cover). Also, assassin helmets should be scaled to fit, as they currently look ridiculous.

Ideally, I would like to see fresh cosmetic (including pets) every season, though I understand that's a lot of work and I don't know if Neocore is able to spend the resources (although the upcoming DLC gives me hope).

Agreed. This would be great to see. FYI,  accidentally downvoted and now can’t change