One kind of game I would like: a game where instead of having all gear being premade, it is built from a variety of objects (valves, grips, resource storage, etc.). Probaby a steampunk-ish setting for all the overengineered bulky stuff people will make.
Picture this: Your support character makes potions. Delivering these to friends/enemies would be difficult, so you design a new main weapon.
You start with a pistol grip, able to hold up 500g of equipment and usable without any aiming delay, but with a negative to ranged accuracy.
To this is attached a Liquid Tap (read: pointy pipe bit) set to point at the target clicked with the device in hand. attached is a Magic two-way pump going to a Vial Slot. The Magic two-way pump is attached to a Tiny magic pickup (set to be connected to the user, though pointing this too at the target would also be an option).
The results: a device that has a swappable potion vial in it and a toggle switch from the pump. Wielding the device and clicking a creature within arm's reach results in a melee attack. If the attack connects to something containing/able to contain liquid (hopefully the creature's body), mana/equivilant magical resource is drained from the user to move a vial's worth into or out of the device, depending on the setting on the pump's toggle. You now have an injector gun! Deliver healing potions to your friends! Poison your enemies! Steal fresh monster blood for alchemical experiments!
Or this: You want a powerful ranged attack using all the cheap ammo you picked up. Therefore you make two items.
The first is a backpack containing a Furnace Boiler (destroy flammable items to turn water into steam) connected to a water tank and a steam tank. The steam tank has a Connector Hose attached.
The second item is a Rifle Chassis with a Medium Projectile Tube on it. Attached to the tube is a Medium Steam-Driven Item Box and both are linked to a Hold-down Trigger Valve going to a Connector Hose.
When both items are worn, the hoses can be connected and the boiler fed with water and wood/coal/paper/etc. objects. Putting a few stacks of Medium Musket Balls in the box on the "rifle" and pulling the trigger will result in the steam rushing from the backpack tank (careful not to overfill it or let it get shot, that could cause an explosion) and into the box and projectile tube. The box will rapidly push the musketballs into the tube where the steam pressure flings them out at the clicked target. You now have a steampunk LMG. Congragulations!
The best thing about such a system is that once the basic framework for resource/signal transfer is in place, content generation is simple, requiring only the definition of a name, image, weight, inputs/outputs, capacities, etc. for most devices. Inputs and end effectors (like the projectile tube that turns pressure into velocity of an item in its [one-slot] inventory chucked at the target of the action) need slightly more scripting, but this should be fairly simple for most items. An item released in a new update may be fairly generic and underpowered for its difficulty of aquisition, but if it has a new size magic storage crystal/whatever, it will open new possibilities for the players, and find its way into the economy nonetheless, even if only for parts.
Armour could use this system too. What about a bracer with a small, battery-powered blood purifyer? Two of those Liquid Taps (or one with fancy piping), a pump, a removable power cell, a series of reagents/filters that separate out/destroy common toxins. Boom, possibly zig-zagging HP and quick poison recovery for the wearer... just don't let anybody shoot out or otherwise smash the "output" tubes... That would be messy.