A couple years ago I posted the following set of Vehicle Design Rules for designing primitive Combat Vehicles and primitive Conventional fighters.
For the most part these rules manage to capture Age of War and Retrotech era vehicles rather closely. There are some off stats but most of the time the difference is normally minor and in my mind the end results are more consistent than using the Support Vehicle rules. Along those lines... Here are the rules... and just about every applicable vehicle and fighter from Age of War, XTRO Retrotech, and the three Primitives books.
Quirks can be found in the original books as not to piss off the Devs.
PRIMITIVE COMBAT VEHICLES
Step 1: Design the Chassis
The following rules changes apply to Step 1 of Combat Vehicle design (designing
the chassis).
Choose Technology Base
As with other Primitives, Primitive Combat Vehicles can only be built using Inner Sphere technology (see Primitive vs. Modern, pp. 144 JS:BD, for exceptions covering "modern Primitive" designs).
They are incompatible with the more advanced technology and construction techniques, such as omni-tech, exotic armor, advanced engines, and double heat sinks as the presence of such technology would make the unit cease to the "primitive". More advanced weapons (and accessories) are an exception and may be used as normal.
Step 2: Install Engines and Control Systems
The following rule changes apply to Step 2 of Combat Vehicle (installing engines and control systems).
Install Engine
The Engine Rating of a Primitive Combat Vehicle is multiplied by 1.2 and the next available engine from the Master Engine Table is used.
Add Engines and Control Systems
Due to the greater bulk and lower technological sophistication of their systems, Primitive Combat Vehicles multiply their tonnage by 1.2, rounding up, when determining the tonnage of their internal structure. Also, because of more primitive life support, detection, and targeting electronics, Primitive Combat Vehicles add 1 ton to the mass of its control systems plus an addition half for every 20 tons of mass.
Add Lift/Dive Equipment or Rotors.
Due to their more rutimentry technology, Primitive Combat Vehicles multiply their mass by 1.2 when determining the weight of their Lift/Dive Equipment or Rotors.
Step 3: Add Armor
Armor for Primitive Combat Vehicles is purchased in half-ton lots and is mounted using the standard limits for Combat Vehicles (see pp. 105-106, TM). They may mount Light, Medium, and Heavy Primitive Armor
Light Primitive armor is statistically identical to Commercial Armor (pp.72, TM).
Medium Primitive Armor has the same number of points per ton as standard armor (16), but is only BAR7 and costs 5,000 C-bills per ton.
Heavy Primitive Armor is statistically identical to Industrial Armor (pp.72, TM).
Step 4: Add Additional Heatsinks
Like modern Combat Vehicles, Primitives may only use single heat sinks and must have a number of heat sinks equal to the total energy weapons heat of the unit.
Step 5: Add Weapons, Ammunition and Other Equipment
Primitive Combat Vehicles may add all weapons in accordance with Primitive Combat Vehicle design (pp. 107-109, TM). However, unless the vehicle is being constructed as "Retro-Tech", such items should be limited to those with an introduction date of 2400 or earlier in order to maintain period authenticity. After that time, engineering had progressed to the point that Combat Vehicles could be constructed using the standard rules for Combat Vehicle construction.
Step 6: Complete Record Sheet.
Primitive Combat Vehicles use the standard Combat Vehicles record sheet. (pp. 109, tm)
PRIMITIVE CONVENTIONAL AIRCRAFT[/u]
Step 1: Design the Chassis
The following rules changes apply to Step 1 of aerospace fighter design (designing the chassis).
Choose Technology Base
As with other Primitives, Primitive conventional fighters can only be built using Inner Sphere technology (see Primitive vs. Modern, pp. 144 JS:BD, for exceptions covering "Modern Primitive" designs). They are incompatible with the more advanced technology and construction techniques, such as omni-tech, exotic armor, advanced engines, and double heat sinks as the presence of such technology would make the unit cease to the "primitive". More advanced weapons (and accessories) are an exception and may be used as normal.
Step 2: Install Engines and Control Systems
The following rule changes apply to Step 2 of conventional fighter design (installing engines and control systems).
Install Engine
The Engine Rating of a Primitive conventional fighter is multiplied by 1.2 and the next available engine (rounded up) from the Master Engine Table is used.
Add Control/Crew Systems
Due to the greater bulk and lower technological sophistication of their systems, Primitive aerospace fighters add 1 ton to the mass of its control systems plus an addition half for every 20 tons of mass; their cockpits functional identically to those of more advanced designs.
Step 3: Add Armor
Armor for Primitive conventional fighters is purchased in half-ton lots and is mounted using the standard limits for conventional fighters (see pp. 190-191, TM). They may mount Light, Medium, and Heavy Primitive Armor.
Light Primitive armor is statistically identical to Commercial Armor (pp.72, TM).
Medium Primitive Armor has the same number of points per ton as standard armor (16), but is only BAR7 and costs 5,000 C-bills per ton.
Heavy Primitive Armor is statistically identical to Industrial Armor (pp.72, TM).
Step 4: Add Additional Heatsinks
Like modern conventional fighters, Primitives may only use single heat sinks and must have a number of heat sinks equal to the total energy weapons heat of the unit.
Step 5: Add Weapons, Ammunition and Other Equipment
Primitive conventional fighters may add all weapons in accordance with conventional fighters design (pp. 194-195, TM). However, unless the fighter is being constructed as "Retro-Tech", such items should be limited to those with an introduction date of 2400 or earlier in order to maintain period authenticity. After that time, engineering had progressed to the point that conventional fighters could be constructed using the standard rules for conventional fighter construction.
Step 6: Complete Record Sheet.
Primitive conventional fighters use the standard conventional fighter record sheet. (pp. 198-199, tm)