Let's talk about Titans. The Titans I'm using in my game. They're gigantic cyborgs, enmeshed with their crew, and designed for specific battlefield roles. There's the Raptor, the Reaper, and the Regent.
The Raptor is a Scout-Titan, which is to say it's digitigrade propulsion is useful for moving the Raptor into forward positions to draw fire. It's a hunter-killer that can, in packs, or from ambush, pull down larger machines. Despite its spare armament and shielding, at close quarters its speed can allow it to outmanoeuvre the big machines. At the other end of the spectrum is the big gun-boat Regent. Massive, with four Titan-class weapon systems and heavy shielding, they're best deployed where their overwhelming firepower isn't interrupted by terrain, or their own colossal size. In between is the main battle Titan, the Reaper, armed with a turret-mounted weapon so that it can plunge into the enemy line, as well as an even balance of firepower, armour, and shielding.
Currently the rules are such that I want the systems of a Titan to be slotted into a System Diagram, currently a 3x3 flat set of squares that determines both where incoming fire goes, and the arc of fire of weapons. This works best for the Raptor, because those have nine systems including a Crew system nestled safely in the middle square. The thing that I'm finding difficult is the decision to either rebuild the notion to reflect the hit diagrams of Epic: Space Marine with a front, back, and side diagram, or perhaps allow systems to be stacked into squares of the diagram, or perhaps even explode the diagram further in 2D to spread systems out horizontally. I also want the Reaper to have a turret for a 360 degree arc of fire for that central weapon pylon mount.
Stacking systems is the easiest way of doing it, having the 'top' system on each stack be the affected system. The ability to re-shuffle the stack lends itself to a certain dynamism. Actually, that captures my imagination, the ability of a Titan to 'change posture' and be able to shift its systems around its diagram, keeping the same orientation and whatnot. It might be an idea to allow Titans to do this as an activation while subtracting a Charge marker from a system to represent the change in posture or configuration delaying the system's charging. In fact it might be an interesting option for the crew beyond being able to repair the Titan, especially since it is primarily useful for protecting a Titan's vulnerable systems.
Which brings me back to the Reaper turret. One way of doing this is simply giving the Reaper a special rule, allowing its central turret mount a 360 degree arc of fire, unlike other weapon systems. It would be nice to systematize it though, as I've always resented the fact that the Battletech Marauder, with its Macross Officer Battlepod design, had a limit traverse on its on huge popgun. On the other hand, I don't recall the Reaver, upon which the Reaper is based, having a 360 degree arc of fire with its back-mount, and it's simply easier to assume that part of making sure these mounts actually work is making sure they don't foul their power cabling and munition feeds by rotating 360 degrees.