Hey there ^^
I suggest that we are able to rank up with Weapons and gain some favours of the Omnissiah, possibly the Emperor himself. When doing certain amount of killing and decapitation of Limbs and Heads, we can earn some Quirks and cooldown reduction for certain skills. This would be Permanent on the Weapon. Also of course when earning Weapons, some would have that or even possible Choice which to have, when you have the Honor to gain a better Weapon you could tell the Mechanicus to tailor towards preference .
This could help some classes like the Librarian to be a even better Crowdcontrol Character and more often played. With his Shockwave that could be Extended in range or build up pon it and have a triple Shockwave when using. Right know hes the hardest to play in his role, since you rely on Axe and Bolter, to be a Psyker and use his skills. Any other setup makes no sense with this class. Psyker skills are the reason you want to play this class, not the Guns!
On hard and No Mercy no one takes Librarian!