Custom rules.

So I'm trying to workshop adding in my own custom grunt unit and want advice.

A squad of 4 Grunts counts as 1 model in terms of getting a team on a board.

The grunts have 1 armor and each grunt is 1 HP, so Everytime you lose HP you lose a grunt. HP restoration items do not restore a grunt.

Grunts have a movement of 1-2

Grunts can spread out but their cubes must be touching, they also stack 4 in a cube but count as a full cube so and ally elite would not be able to join their cube and if an enemy assaults their cube one grunt is knock backed out of the cube. If the knock back is into a wall or off the terrain then they are killed. Grunts have 7+ on their fight, but on assaulting they can trigger a suicide which kills the grunt performing it, but does 2 plasma grenades worth of damage that don't have to roll to see if they succeed hitting the cube.

They are equipped with a plasma pistol that has esd +1 and 0 ap they hit 6+ or can overcharge for a long action and esd +4. Each grunt takes their own independent shooting action along with the bonuses they specifically have. They also have keyword horde. They each have one plasma grenade.

So any advice on editing their rules, how their score would work? How would they interact with picking up weapons or items? Are they overpowered, underpowered?