I thoroughly enjoyed the game and am looking forward to the full project.
I like the enemy variety both biological and mechanical. I also particularly enjoy that you included a collateral damage aspect that accounts for your precision or lack thereof. I think the various damage types that you deal and receive are also neat- Tank feel punishing if you don't stay mobile.
I thoughts regarding potential armaments:
Primary Weapon:
A Main Battle Tank type gun: 120-125mm Munitions with Low to Medium Sized Magazine Capacity. Fire Rate: Medium to Slow. Damage: Medium to High. Knock Back Low to Medium. Penetration: High
A Direct Energy Weapon/"Beam": Battery-Based; could be tied to an overheat mechanic. Maybe Three-Four Batteries in Magazine. Fire Rate High/"Continuous". Damage: Low to Medium. Knockback: Medium: Penetration: Very High.
Secondary Weapon:
A Multiple Missile Launch option: This option has the missiles follow an arched ballistic trajectory, similar to the grenades- as another way to go over buildings instead of through or around them. There can be a High Explosive Unitary Warhead option or a Cluster Munition option.
I have seen some other suggest Mortars; I think Mortars or Artillery (Cannon-based) are good options as well. Taking the same concept as mentioned in the Multiple Missile Launch Option- Think Mortars and Artillery can be implemented in the same way. The difference being Mortars have less range, more fragmentation/damage to soft targets vs Artillery having greater range and some damage on armored targets.
An Anti-Air Option: A dedicated guided surface to air missile might be interesting based on potential future missions or play styles
Grenades:
A Thermobaric Option: Explosive with High Knockback, less damage than standard HE against armored targets but very effective against soft and light armored targets.
Scatterable Mines: A grenade that scatters mines similar to the smoke grenade currently functions
An EMP Option: Mechanically functions as a "stun" grenade but allows for better positioning for less collateral damage
Fun Option- Something similar to the M58 mine-clearing line charge (MICLIC).