While Tri-Stat dX is a complete set of free RPG rules, the Own a Big Mecha Attribute is somewhat anemic. That's something one of the game's designers, David L. Pulver, addressed in a posting to the old GoO forum. Here are the revised Own a Big Mecha rules he published there.
Own Big Mecha Attribute
Revised version by David L. Pulver
My thanks to everyone who responded. Here is a slight revision and clarification of the Attribute. Comments are welcome. As before, note that this is not (yet) an official rule.
Own a Big Mecha (OBM)
Cost: 8 points/level for 10 or 16 points
Relevant Stat: None
Required PMV: None.
Optional PMV: None.
Progression: Linear; +10 or +16 Character Points for vehicle building each Level
Reduction: Fewer Character Points awarded
Restrictions: Mecha belongs to agency; Mecha is stolen
This is an alternate open-ended way of building mecha and other vehicles using the OBM Attribute that provides additonal flexibility.
Each level of OBM gives 10 or 16 Points to build a mecha, which may be any kind of suit or vehicle that a person can ride in or on. A default mecha is assumed to be anthropomorphic but a mecha can be anything from a row boat to a 100' tall giant robot to a starship -- just assign appropriate Defects.
A mecha is always assumed to be too obvious or awkward to easily carry in many social situations, such as a bicycle or a suit of bulky armour, or most vehicles. If a mecha is small enough to be worn or carried socially, like a pair of roller skates or a light or invisible armour suit, it should be built as an Item of Power instead. If a mecha is a form-fitting suit worn rather than ridden or driven, it can be built with these rules but each Level only grants 10 Character Points (matching Item of Power) instead of the usual 16 Character Points.
The mecha is created just like a character, with two exceptions that differentiate it from someone created via the Servant attributes: it has no Stats and its occupancy and land speed are determined as shown below.
A mecha must be piloted by a character to operate it. The mecha's operator uses his or her Stats when the mecha must make a check. If a mecha has multiple occupants, only one operator can control it at any one time. Other passengers are just that, unless the mecha has specific attributes that assigned to other crew (see below).
In addition to normal attributes, two specific Attributes can be bought for the mecha using its Character Points: Capacity and Land Speed.
Land Speed costs 1 Point/Level. Each Level gives the mecha the ability to move on the ground (via wheels, tracks, legs, etc. – you decide). The speed is found using the Slow Progression chart beginning at 30 kph. A mecha with no levels of Land Speed cannot move on the ground; it is stationary, like a boat or base.
Capacity costs 1 Point/Level. It is the amount of space inside the mecha for occupants and passengers. Refer to the Targets column of the PMV chart (dX, page 10) to determine capacity. For example, Level 1 capacity is 1 person or 50 kg. Distribute it between people and cargo (at 50 kg per human-sized occupant).
If no Levels of Capacity were assigned, the mecha can still carry one person, but it is small enough that any damage that penetrates its armour also applies to the wearer, although his or her own armour will protect. This might be a form-fitting suit, a racing car, or other tight-fitted design.
A mecha may be given just about any Attribute. In particular, the Flight, Hyper Flight and Water Speed Attributes will allow it to operate in various environments. Mecha will usually not take the Speed Attribute, but it may be appropriate for certain types of designs, such as a suit that enhances reflexes.
Armour and Tough are common. A mecha must be given at least as many Levels of the Tough Attribute as it has Levels of Capacity. If the mecha can manipulate things, giving it equivalent levels of Superstrength is a good idea. The operator's own Body is used for Body checks, modified as usual by Superstrength.
A mecha's Attributes are used by the operator and occupants when dealing with the world outside the mecha. Attributes Attacks and other Attributes that affect specific targets can only be used by one of the mecha's occupants. Other Attributes, such as Adaptation, will protect the occupants along with the mecha itself.
Attributes are usually used by a single operator but may be assigned to other crew when the mecha is designed. For example, a starship might be built with the Hyper Flight and Flight Attributes with one assigned to the "pilot" and the other to the "navigator." Occupants other than the primary operator can only attack from within a mecha if it has additional Special Attacks that are assigned to them. If such a "different gunner" uses a mecha's weapon, the operator cannot use it in the same round.
Attributes that a mecha has do not usually stack with those of a character. If a mecha has Flight Level 1 and so does its operator, this does not give the mecha Flight Level 2, for example.
The GM may make exceptions for mecha bought using the Item of Power Point progression (10 points/Level of OBM). Thus, a powered suit designed for a dragon (which already has Superstrength and Flight) may add its Levels to the dragon's own abilities.
Vehicle computes can be simulated by giving the mecha the Highly Skilled Attribute. For play balance, it is suggested that a mecha not be able to grant more than 2 levels.
A mecha should be given Defects to reduce its cost and define its capabilites. The effects of these Defects only apply when the mecha operator or other occupants are trying to manipulate, perceive, or affect the outside world. For example, if a mecha has Sensor Impairment (to vision), the occupants cannot see out. They can still see normally inside the mecha. Similarly, Physical Impairment (no hands) -- which most non-anthropomorphic vehicles will possess - means the vehicle has no ability to lift, punch, and so on, but doesn't affect the driver if he or she wants to scratch an itch or pull out a cell phone.
Since mecha have no self-awareness, a Defect that assumes the mecha has a mind, soul, or personality is inappropriate unless it could be plausibly extended to the occupants. Thus, Blind Fury, Significant Other, or Recurring Nightmares would not fit unless (for example) the mecha has some form of neural interface system that influences its crew's mentality, a concept that does occur in some giant robot anime (for example). On the other hand, the Owned Defect is not normally appropriate to a mecha. Instead, the character (not the mecha!) should take the Conditional Ownership Defect linked Own a Big Mecha. A Defect like Famous, Red Tape, or Wanted could be assigned to a mecha, however.
For realism's sake, a mecha should have at least as many Levels of Awkward Size Defect as it has Levels of Capacity. Likewise, a mecha should only have Diminutive if the standard occupants are appropriately small.
Required Skill: Assign the mecha a required skill, e.g., Driving if it has Land Speed, or Piloting if Flight or Boating if Water Speed. This is the skill used to operate it. A character may operate a mecha without having the appropriate skill, if the GM believes it is relatively simple (e.g., driving a car). Some mecha may require multiples skills for different functions such as sensors
Gadgets and Mecha Points: Each major gadget can be traded for 4 Points to build a vehicle, or to augment an existing mecha to create one of intermediate power.
Servants and Mecha: Intelligent mecha are built as Servants or characters. The GM may optionally allow the Land Speed and Capacity attributes to be taken by Servants. If Servants have Capacity, the GM should rigidly enforce the requirement for mininum levels of Awkward Size (a Servant could, of course, have an Alternate Form that was large enough for Capacity).
Example of 4-point Vehicle
Capacity 2: (carries 4 people and 100 kg) (2 points)
Land Speed 4: 250 kph (4 points; Restriction: Land speed only on road (-1 point).
Armor 1 (unarmored area, -2) (1 point)
Tough 3 (60 Health) (6 points)
Awkward Size 2 (-2 points)
Special Requirement 1 (machine: needs fuel to run and requires repairs to heal) (-2 points)
Weak Point (gas tank, -1 point)
Physical Impairment (no arms, -3 points)