For a while now I have planned to expand the range of systems available for Titans, mainly by making sure that the core 'engine' of the game was robust enough that I could add new content that expanded on existing rules and structures rather than adding new mechanics. Some of this was pulled back from the version that was Kickstarted, and some of this relates to the utility buildings that have been pulled back from the online versions. I should start working on it again, as I feel really good about how the core game is working now.
Configuration Cog: This was intended to allow players to move their system tokens around in their Titan System Diagrams, and maybe even swap out systems for other systems. It's difficult to implement online when the System Diagrams are not modular anymore. Nonetheless, it's possible that it could give a Titan a second Dashboard, essentially switching it out so that the Titan has a second mode composed of the same number of systems with the same configuration of damage and shields. Enable your Titan to transform...
Teleporter: Jump Jets are fun, but in terms of movement it would be fun to have a system that allows a Titan to move itself freely around the board. The tricky part is essentially how this differs from jump jet systems, aside from a greater freedom of movement, and what the cost of doing so might be.
Holographic/Stealth fields: This is fun from a design standpoint as there is already an established set of rules and mechanics for stuff being located on the board, sensors and the placement of buildings. I think it would be interesting to have both some interaction with the sensor system, and also a form of blocking rather than replicate essentially what a teleporter would do, which is to reposition the Titan on the board. One suggestion, easily implemented online but less so in meat-space, is to simply have multiples of a Titan figurine on the board. My idea would be a system allowing a Titan to block attacks using nearby buildings rather than, say, its own onboard systems.
Drones: Because having an additional little widget wandering around the board doing stuff for a Titan would be both an entertaining feature, and should dovetail nicely with the implementation of 'conventional' forces of infantry and tanks and whatnot. Essentially the drone would have some actions (move/attack, move/detect, move/shield) that it could do while its Titan is safely away.
Passive Onboard Systems: One thought was to have systems that cannot be activated to do anything, but that exist to bolster existing systems, such as to increase the number of cards drawn, decrease the cost of charging systems, increase the effect of systems, or to otherwise given a Titan's active systems a bonus rather like how Extra Armour has the Telemetry rule.
Expanded Existing Systems:
Limbs: There's space for new kinds of limbs, and even stuff that's limb-like, like tracks and other motive units. There's certainly space for weak, stubby legs, and for tentacles or flexible arms like cephalopods.
Weapons: Likewise there's space for a range of weapons, particularly missile weapons can be expanded beyond the rocket pod, and additional space for traits that enable things like ignoring line of sight, doing weird things with range, and especially stuff like swords, axes, flails, lances, and even shields (as extra armour/shield hybrids). That is, after all, why I re-jigged the Dashboards so that systems can be added on top of other systems, provided a certain kind of weapon with a certain trait is present to hold them.
Jump Jets: Given how these things are numbered, and how they've developed (capacitors I'm looking at you) I think it's probably worth rationalizing Plasma Capacitors/Plasma Cells as simply Capacitors 1 & Capacitors 2 too. Likewise Thrusters 2 and Plasma Jets 2, and maybe call the Thrusters 'Plasma Thrusters' or some such. Someone suggested having retro-thrusters would be handy, as being able to jump backwards over an opponent could be useful at the moment. I've also thought it would be neat to have Wings or somesuch, enabling something of a hybrid between jump movement and walking movement.
Extra Armour: Likewise, being able to pile on some more Extra Armour (4, 5, etc), and maybe just some variations on it, like the aforementioned Shield enabling both shield tokens and blocking.