It is armed with an M274 140mm electro-thermal cannon system as its main weapon and a 35mm M32 coaxial cannon for softer targets. A sub-turret has a dual 15mm machinegun system for anti-infantry defense and a light laser for defense against missiles and aircraft/spacecraft. Hardpoints exist for various rockets and missiles, while the turret features a 90mm mortar system for light fire support. The treads were designed in such a way to have redundancy. Its quad tread system has four clusters of two treads to a cluster. The whole tank can operate on just four treads if one from each cluster were destroyed. While this tread system is complex and requires a lot of maintenance, it has saved lives by allowing the tank to escape an otherwise crippling blow.
The M35 is currently being upgraded to the Mk. 4 configuration. Among the upgrades is a retractable mast-mounted sensor system that will allow it to survey the area while in a hull down position. An improved fire control to allow it to use the main cannon against dropships, strike ships and assault landers (which are incredibly resistant to conventional anti-aircraft weapons due to their sheer size and mass). A new suspension system will reduce strain on its treads, allowing for reduced maintenance downtime while a faster auto-loader will increase the M274's rate of fire to one shot every two-point-four seconds.
I forgot to state that it is powered by an air-indepedant system. Not too much different than what some modern non-nuclear sumarines use in real life. All the vehicles in my novel (includng mechs) use air-independant systems because not all planets have oxygen atmoshpheres (many planets have no atmsphere at all).