So I was talking over artillery support for a non-canon unit up in that forum, and articulated the idea of using an aerospace fighter as part of an integrated "shoot and scoot" system.
Here's what I have so far (I don't have HMAero):
Winged Caisson
Tonnage 60.00
Cockpit 3.00 200,000
Life Support 50,000
Sensors 120,000
SI 250,000 (5)
Attitude Thruster 25,000
Landing Gear 600
Engine 7.00 720,000 (5/8)
Fuel 5.00 1,000
Armor 13.50 135,000
HS 20,000
Weapons 2.00 80,000
Comms 3.00 30,000 (4 tons total: can leverage satellites; adds three crew)
Field Artillery Bay 15.00 0
Ammo 4.00 0
Infantry Bay 7.00 105,000
Paramedic Gear 0.25 7,500
Exo Compartment 0.25 0
Sub Total 60.00 1,744,100
Multiplier 1.30 2,267,330
The Thumper itself weighs a straight 15 tons, and costs 187,500 C-Bills.
For simplicity's sake, I made the "Infantry Platoon" a Motorized Rifle Platoon, though the Thumper only needs three of the squads. I'm fluffing the fourth squad as being the Pilot, Communications Specialists (3), Medics (2), and an Industrial Exoskeleton operator.
The platoon costs 801,407, and is armed with 28 Auto-Rifles. When I get around to refining this concept, some of them will be replaced by Intek Laser Rifles, and everyone will get a decent set of armor. I'll also properly account for the cost of the Medics.
The industrial exoskeleton is a bare chassis with 3 MP and a one ton lift capacity (so it can pick up a full ton of ammo at a time). I gave it 3 MP so it could keep up with the Motorized Troops if/when they abandon the gun. It weighs 250 kg and costs 252,000 after adding in the 150,000 training cost for the pilot.
A whole system costs 3,508,237 and requires 28 personnel. That's 21,049,422 C-Bills and 168 personnel per battery of six guns. Not bad for a Thumper that can be flown around at 5/8.
A minimal shoot and scoot cycle would be 30 seconds:
Turn 1: Fighter lands, Gun dismounts
Turn 2: Gun fires
Turn 3: Gun mounts, Fighter takes off
In practice, the gun could probably get off a bit more of a fire mission than a single round.
EDIT: Corrected some math errors I just caught...