Alright, so I'm in the process of mulling over house rules/setting modifications for mecha combat. Particularly I am going to be running a game set in the Gundam universe (UC).
I'm considering this different from the Battletech topic, as thematically Battletech tends to represent slower and heavier fights. I did consider making the entire game such that the PCs are actually their mechs; that I would just use the personal scale rules, state that sil 1 = normal sized mech. The problem is I do also want to account for PCs who are not mech pilots (have at least one), as well I desire for mechs to be rather standardized (i.e. some players are piloting Zaku IIs, and some are piloting GMs).
The main issue I'm running into is how to deal with Speed. This sort of combat, while often depicted as fast paced, is also characterized by rapid deceleration, and often outright stops. Speed as a vehicle mechanic makes sense for cars, planes, and naval ships, but not so much for vehicles that are basically in the form of humans. I would prefer to not force my players to constantly be making accelerate/decelerate maneuvers. Note that some maneuvers/actions (mainly Evasion/Gain the Advantage) have minimum speed requirements that also don't mesh well. I really need my PCs to be able to rapidly move to a location in one turn, and then in the following turn be able to duke it out in a specific area without moving much. All while offering a full action economy (instead of forcing them to spend full turns speeding up/slowing down).
Next up, survivability. While there is the option of Barrel Roll, there really aren't any other options presented in the core book. As vehicle melee combat isn't a thing, there isn't even a notion of parrying. I intend for vehicle combat to take up a larger section of the game, and as such, would want to ensure better long term suitability.
To top it off, I do still intend to run with tanks, aircraft, and other capital ships (i.e. things that play nice with the current rules), so it doesn't quite work for me to gut and change the vehicle rules; I still need to be able to run normal vehicles.
Currently, what I've come up with is the following:
QuoteVehicle Trait "Mobile Suit"
-This vehicle is always considered to be at its maximum speed. Instead of having forced movement based on its Speed, this Vehicle instead moves by using the Reposition Maneuver. When using Reposition, instead of moving only one range band, use Table III.2-14 to see how many Range Bands this Vehicle can move. As well, this Vehicle ignores Minimum Speed requirements on all Maneuvers/Actions.
-As this vehicle is basically in human form, it benefits from any talent its pilot has that works on the personal scale. Essentially any talent that uses the word "character" can interchangeably be used with the vehicle itself. If the talent has a strain cost, then to use it the pilot suffers strain as well as the vehicle suffers an equal amount of system strain. However if a talent recovers strain, the vehicle does not recover system strain (and apply the same logic with wounds if such talents exist). When dealing with damage, replace Soak with Armor appropriately.
-When piloting a mobile suit, other mobile suits are not considered "vehicle" targets.
-Mobile Suits are considered to have Brawn equal to their Armor. The Piloting skill is still used to test across the board, but in cases where the actual strength of the unit is in question (e.g. picking up rocks), the ruggedness of the unit is used in place of the agility of the pilot for the test.
-Mobile Suits have the ability to engage in melee combat. For hand to hand, use the base unarmed attacks (using Armor as Brawn for base damage, plus the profile for the qualities). Melee weapons for Mobile Suits work similarly to melee weapons for characters, in that its a +damage profile that determines base damage by adding Brawn (in this case Armor)