The majority of mecha, especially those in the Atlantic Federation, have two hardpoints on the upper rear torso or shoulders. These twin points can be used to add an additional equipment pack onto the rear of the vehicle, for varying purposes. These are not straps over the shoulders going back to school bookbags, but rather large pieces of bolt on equipment.
1. The Refrigerator
The Refrigerator is a supplemental cooling system that feeds into the mecha's existing coolant system. The 'fridge' has both additional heat sinks, but also has radiator fins for faster heat transfer. This can easily double the cooling capacity of whatever mech it is linked to. This is a popular mod for mecha that are heavily armed with laser and plasma weaponry, or are deployed in literal hot spots.
2. The Supercharger
Some mecha, especially larger mecha, can struggle to have enough power to keep their locomotor systems and weapons running at the same time, and many machines will have a smaller powerplant to manage weight and housing said systems. The Supercharger is a power booster that can boost the machine's available power in high demand situations. This can keep a power hungry mech stay in a fight, or it can let a larger mech boost it's cruise and flank speeds, for a short time. This can be a surprise in combat, and can be devastating for mecha that deploy powered melee weapons and enter close quarters combat.
3. Hornet System
A Hornet system is a drone carrier, specifically an armed drone carrier. The typical Hornet drone has a medium laser, or a short range missile system. While not devastating alone, a foe facing a mech armed with the Hornet system can find itself constantly being sniped from behind, in the head, or constantly being flanked. This can exploit thinner armor, and can distract from fighting the actual mecha launching the hornets.
4. Armor Tunic
Hooking to the back points, the armor tunic is draped across the front of the mech and covers the vulnerable back and hip joints. While heavy, this armor shroud can provide significant protection from critical hits. a mech with this shroud and a shield can wither an incredible amount of incoming fire. This is uncommon as it is considered unsexy, and it is heavy and impacts the machine's speed and agility.
The Wolfmother backpack is really kind of horrific. The backpack is a drone carrier, but it carries a LARGE number of arachnotrons. These war spiders are armed with shaped charges, plasma knives, and short range flechette guns. These can be deployed to swarm across a battlefield, or if a mech goes into close quarters, the spider bots can leap from their host onto the enemy machine and wreck havoc there.
The Hackpack is a mobile cyber warfare system. The pack contains a military Limited AI (L/AI), a CogNet transmitter system, and a remote hacking system, allowing the combat AI to hack into enemy communications, compromise it's intel systems, and even employing proxy hacks on augmented enemy personnel. These packs are expensive, and delicate. They are normally mounted on stealth and recon mecha. A Hackpack can also double as a mobile communication center, and can handle all the data and routing needs of a combat division in the field.
7. Doombud System
When you need to make a statement, few things speak louder than detonating an austerhagen device in the middle of a battlefield. Normally deployed in a drone, the Doombud is a large warhead mounted in an armor shroud. This turns a single mech into a WMD often only needing to get into a vulnerable area and self destructing.
Additional Ideas (1)
While it is not the best idea to put ECW gear on mech, there are many cases where one of these on an assault mech can go a long way.Assault mechs are the only ones that can carry these as their size is to big for lesser mechs.