It would be nice to see some bolter ammo variation in the game, either as seperate weapon entries or something you can change about your weapon with Hadron (for a fee).
Kraken bolts - Solid shot, no explosion, very high pen.
Dragonfire bolts - Flame burst, no explosive core, reduced damage, stagger. Releases a ball of flame (5m radius) on impact as well as setting the target on fire with direct hit. Anti-Cover.
Giving the Psyker access to the Bolter would be my next step, allowing them to take a bolter with Psi-Bolts. Psi-Bolts being particularly good at killing daemonic enemies. BoN, Host etc
Psi-Bolts - 3% peril per bolt - Psychic explosion on impact as well as regular bolt explosion.
Headsplitter Psi-Bolts - 6% peril per bolt - Same as kraken plus cause instant brainburst (weak) (free from building perils meter) on hit.
Bonus: Swap shotgun secondary for a single slug with high pen instead of horizontal spread.
A change to the bolter to be able to switch fire rates from hip and ads would also be welcome.
Remove bolter racking animation on swap or at least change this to auto reload if you swapped your weapon when it was empty. So fire bolter til empty, swap to melee, swap back to bolter reload animation begins skipping initial racking.