Smite: Add a new node that changes smite primary fire or just outright change the primary fire into a heavy peril cost ability that shoots a strand of biolightning that lingers for 1-3 seconds on the foe after the casting is stopped, remaining as a “spreading point” to nearby enemies, this allows for hybrid combat with smite since you can now blast them with the “ball of lightning” and switch to your other weapons.
Smite: Add a new node or change Enfeeble to grant Brittleness stacks to the affected targets. This would allow for more hybrid combat and more build variety.
Brain Rupture: Add a new node or change it baseline that brain rupture deals Brittleness to the target for a duration, allowing for better hybrid combat and cooperation. This can be accompanied by the old +25% damage dealt by non-warp attacks for 5 s to the target, or that could be brought as another new node. This way you make hybrid combat more interesting.
Brain Rupture: Change the ability to cause damage to enemies during the casting over time, so that friends shooting the brain rupture target do not entirely waste the casters time. If you want to be especially nice, you can make it so that the ending “pay-off” damage is charged up over time, and each time that the ability causes a tick of damage before the casting ends, the game checks if the currently charged “pay-off” amount WOULD be enough to kill the target, in which case the “pay-off” triggers prematurely and the casting ends, so you do not need to use the full duration to finish off enemies. This would feel extremely satisfying and retain the same level of DPS for the ability. If you want do compensation for this buff for the pre-charge option, you can always allow for maximum movement speed AFTER the secondary fire is fully charged and you can reduce the amount of peril cost it takes to maintain a fully charged secondary charge option to something like 1 peril per second, allowing for more fun and fluid and fast paced combat!
For example: Brain rupture deals 40 damage each tick, and a tick occurs every 10% and then the “pay-off” increases by 80 damage each tick, so a brain rupture would deal a total of 1200 damage (this total sum can be tweaked!). Now: an enemy has 600 or 550 hp, so it takes 200 damage from the ticks during casting, but then at the 50% point the rupture “pay-off” amount gathered thus far: 400 (80dmg x5 ticks), would be enough to kill them (400 hp or 350 hp remaining whichever example you want) then as the damage WOULD be enough to kill them the pay off triggers and the peril cost of the ability is completed.
Further discussion: A good way to think of the “pay-off” gathering but only being dealt as damage is as pressure building up until a breaking point is reached, and the damage that each tick does can be thought of as the damage the pressure does due to it tiring and straining the material (skull). I think this way brain rupture would be far more satisfying to use and would imitate the fantasy better, plus it would remain as simple to use as previously, if not simpler. Even though the mechanics behind an ability can be multilayered it does not mean that the play is unwantedly complex due to that! 
NOTE: any increase in damage can be adjusted with reducing some of the “pay-off” damage! But I would advice against reducing the effectiveness of one of the already less fun options.
Brain Rupture: Add a new node: Skull Shrapnel to Brain Rupture, which causes kills with Brain Rupture to explode with a small area of effect, damaging nearby enemies. This additional node could allow you to kill hordes and tightly packed shooters with some success. The aoe should be large enough and the explosion damage strong enough to outright kill 2-4 additional horde enemies in a dense horde or 1-2 additional shooters who take cover behind the same cover, something like a radius of 2 to 2.5 meters. This node could have an internal cooldown, and it could require you to completely charge the ability with the secondary fire to activate it, so that the player can control the node’s use.
Venting Shriek: Add a new node or change Warp Rupture into a high damage high cleave beam that can be used either to sweep horde or deal good damage to monsters, this is a cool fantasy and requires skill to be efficient with (if you make it heavily headshot dependent). If it is really headshot dependent it could be named “Mindmelting Ray” or some such.
Further Discussion: It could be cool to have the Ray expend a sum total of peril linearly over the time it is active, such as over 3-4 seconds, so that it looks like you are venting peril into the formation of the ray. This amount of peril could be 50% to remain in line with the baseline. Even if you gained more peril during the ray, it would still only vent a sum total, so it would not be that strong. This ability could also be made so strong and potent that it would warrant the cooldown of the ability to be considerably increased.
Venting Shriek: Add a new node or change Warp Rupture to Ruin Weapons, a psychic ability that breaks enemy ranged weapons internally. This is an established, very lore friendly ability. This would force ranged enemies to either wait out a potential duration or be forced to do a melee rush.
Scrier’s Gaze: Since the ability has effects more befitting a name such as “Biomancer’s Fury” we could have the Scrying part of the ability be reflected with effects that reveal enemy heads as small sparkles in your field of view, that you can see through walls, but which are larger and brighter when you have an open sightline to them. This way it does not flood the screen, and it indicates all the heads you can shoot, more reinforcing the scrier fantasy, and being a good combo to disrupt destiny and precognition. This ability can be a new node, to make it be balanced, since now it costs more points.
NOTE: Since this ability does not reveal enemies by TYPE the guardsman’s executioner’s stance remains valid as it gives different information!
Peril Generation Reduction Nodes: These nodes should always have a sister node that allows you to not take them, such as health, toughness damage reduction and similar. This is because some psykers do not want their peril level management crippled, and allows for more tinkerability, some may like peril generation reduction, some may do not want it, so this is a nice way to have both parties pleased.
Assail: Add a new node: Bewitched Arsenal, using Weapon Special whilst wielding assail and having all 10 shards expends all shards and gives you an equally large stack of Bewitched Munitions. (Bewitched Munitions stack maximum size is 10.)
When you have stacks of Bewitched Munitions: fired bullets and lasfire that would stop instead ricochet to one additional nearby enemy’s head. A bullet or lasgun shots “stop” due to hitting enemies or enough enemies if the shot penetrates targets or due to hitting a wall.
You lose 1 stack of bewitched bullets for each 1% of the magazine of your ranged weapon that you use whilst you have stacks.
Further Discussion: This means sacrificing 10 assail shards gives you 1 Bewitched Munition use for Revolver (5 ammo in magazine, so 1 bullet uses 20% so all stacks are used) and 2-3 for Vraks 7 (18-22 ammo in magazine, so 1 bullet uses about 4-5% of ammo so all stacks are used after 2-3 shots).
You could also give Bewitched Munitions follow-up nodes that allow the munitions affected by it to have High Rending or perhaps that kills made with Bewitched Munitions have a random chance to give you a small amount of ammo back.