Right, some unit templates.
Infantry
Garrison Troop.
Armour: Light Infantry Armour (AR1)
Slot 1: Light Personal Weapons (Size: 4, AP 5, Dmg 10, Shots 1)
Special Training: None
Generally comes in three types of formations; large garrison formations on low priority worlds that should still have a dedicated garrison force to either quell the threat of riots or as insurance, smaller formations that can be carried by troop transport ships for the purpose of pacifying newly conquered worlds, and finally as security for early TN high value unit like STO units and Bombardment units. These troops are cheap, quick to train, and numerous, making them excellent at freeing up more valuable units for frontline duty. Once Power Armour becomes available it's common for these units to be replaced in the security role by line infantry.
Line Infantry
Armour: Light Infantry Armour (AR1) or Powered Infantry Armour (AR2)
Slot 1: Personal Weapons (Size 5, AP10, Dmg 10, Shots 1)
Special Training: Uncommon
The most common combatant of the various militaries, a decent all rounder but no real specialty. These make up the bulk of any deployed force. Although equipping all of them with cutting edge power armour technology is too expensive to be sensible, as such technology develops it becomes more available. Forces intended for specific planetary theaters may find themselves with specialist training programs for unusual combat conditions.
Weapons Team
Armour: Light Infantry Armour (AR1) or Powered Infantry Armour (AR2)
Slot 1: Crew Served Anti-Personnel (Size 12, AP 10, Dmg 10, Shots 6) or Heavy Crew-Served Anti-Personnel (Size 20, AP 20, Dmg 10, Shots 6) or Light Anti Vehicle (Size 16, AP 20, Dmg 60, Shots 1) or Light Bombardment (Size 20, AP 10, Dmg 10, Shots 3) or Light Anti Air (Size 20, AP 10, Dmg 20, Shots 1)
Special Training: Uncommon
A grouping of support units for infantry formations, you usually find these integrated with the formation they are working with, except for Bombardment units which may be detached into a smaller formation due to game mechanics. There's usually no more than 1 Weapons Team per dozen infantry units, and often less than that, but at least 1 per 50 except for Garrison Troops, which may have fewer.
Special Forces
Armour: Light Infantry Armour (AR1) or Powered Infantry Armour (AR2) or Heavy Powered Armour (AR3)
Slot 1: Any infantry weapon
Special Training: At least 1, often more.
The expensive but very competent option, these forces usually operate in the best armour available and have been trained for expected unusual combat conditions. They otherwise generally reflect their military's infantry doctrines in their operation and organisation. Formations with more than 3 specialties are very unusual as they are very expensive, but the flexibility may be worth it.
Forward Observer
Armour: Light Infantry Armour (AR1) or Powered Infantry Armour (AR2) or Heavy Powered Armour (AR3)
Slot 1: Forward Fire Direction (Size 60, Special)
Special Training: As embedded formation
Forward Observers guide the fire from Bombardment units and ships, and are usually attached straight to the relevant HQ section.
Vehicle:
Armed Transport
Light Vehicle (Size 12)
Armour: Light Vehicle Armour (AR2)
Slot 1: As Weapons Team, swap Light Bombardment for Light Autocannon
A common sight on the modern battlefield, various forms of armed transports are used to quickly move troops around to respond to shifting battlefield conditions. Most are armed with a crew served anti-personnel weapon mounted on top, but it's not unusual to find light anti armour or anti air weapons mounted on them instead. Although Garrison formations usually have few to none of these vehicles (instead using unarmed and unarmoured vehicles that are sufficiently a liability in combat they are not rendered in the engine), other infantry formations will have 1 for anywhere between 5 and 20 infantry units.
Formations.
HQs are inserted as necessary. It's presumed that only 1 HQ is needed of a given rank. Although the Artillery Formations call out the size of their security section, it's presumed that Battalion HQs have a platoon sized security section (30 infantry, 3 weapon teams and 5 Armed Transports) and higher HQs have a security section the size of a Company
Garrison Company
HQ 1250
160 Garrison Troops
4 Crew Served Anti Personnel Weapons Teams
4 Armed Transport with Crew Served Anti Personnel
Total Size: 814
Garrison formations fluctuate considerably in size, but should for ease of counting be considered to be made up of discrete chunks of 40 Garrison Troops, a Weapons Team and an Armed Transport, which is approximately Size 200. Garrison formations are unlikely to have dedicated anti vehicle, anti air or bombardment weapons. It's just generally not needed or too heavy to use in the sort of engagements garrison troops get involved in. If the sort of opponent is expected where such weapons are needed it's preferred to shift dedicated front line combat troops in as reinforcements instead.
Garrison Battalion
HQ 5000
800-1000 Garrison Troops
20-25 Weapons Teams
20-25 Armed Transports
Garrison Regiment
HQ 20k
3000-4000 Garrison Troops
80-100 Weapons Teams
80-100 Armed Transports
Garrison Corps
HQ 250k
30 000-50 000 Garrison Troops
750-1250 Weapons Teams
750-1250 Armed Transports
Garrison Army
HQ 4m
200 000 - 800 000 Garrison Troops
5 000- 20 000 Weapons Teams
5 000- 20 000 Armed Transports
Garrison Armies are unlikely to be seen in any game, but could be found on densely populated planets occupied by a high militancy government away from the frontlines. Most other governments would keep smaller garrisons.
Line Infantry
Line Infantry Formations come in two varieties; generalists, and those specialized for 1 or 2 terrain features (Mountain/Jungle is always popular). While modern day thinking would consider forces specialized to fight, for example, in the mountains as a special force unit, I'm fairly arbitrarily making a distinction here between 'line units with special training' and 'special forces.'
Line Infantry Company
HQ 1250
80 - 140 Line Infantry
8 - 14 Weapons Teams (at least half with AP, remainder mixed anti vehicle and anti air)
8 - 14 Armed Transports (Mix)
I am presuming a mix of 10 Line Infantry, a Weapons Team and an Armed Transport as a basic unit, giving a range of 86-102 as its size.
Line Infantry Battalion
HQ 5000
320 - 560 Line Infantry
32 - 56 Weapons Teams
32 - 56 Armed Transports
1 Forward Observer
Line Infantry Regiment (Artillery heavy)
HQ 20k
960 - 1680 Line Infantry
96 - 168 Weapons Teams
96 - 168 Armed Transports
3 Forward Observers
Attached Artillery Company
Line Infantry Regiment (Artillery light)
HQ 20k
1280 - 2240 Line Infantry
128 - 224 Weapons Teams
128 - 224 Armed Transport
3 Forward Observers
Line Infantry Division
HQ 50k
2000 - 3000 Line Infantry
200 - 300 Weapons Teams
200 - 300 Armed Transports
5 - 8 Forward Observers
Attached Artillery Company
Potential attached heavier artillery battery (4 - 12 Vehicle/Static Medium Bombardment assets)
Generally no heavier Formations than this will be expected to operate independently, such formations are likely to be more ad hoc, attaching Division and lower units to an existing core of a high ranking HQ, it's immediate security and its own support assets, including heavy weaponry formations.
Motorised Artillery Company (Size about 950 max)
HQ 1250
40 Garrison Troops/Line Infantry (Security section)
4 Weapons Teams (2 anti personnel, 1 anti vehicle, 1 anti air)
12 - 18 Weapons Teams Bombardment
10 - 13 Armoured Transports (Mix of anti personnel, anti vehicle, anti air, auto cannon.)
Mechanized Artillery Company (Size about 1200 max)
HQ 1250
40 Garrison Troops/Line Infantry (Security section)
4 Weapons Teams (2 anti personnel, 1 anti vehicle, 1 anti air)
8 Armoured Transports (Mix of anti personnel, anti vehicle, anti air, autocannon)
14 - 22 Armoured Transport (Light Bombardment)
Special Forces
Special Forces are unusual for two reasons; for one, they are always specialized in some way and have access to the equipment to cope well in such circumstances. For another, Special Forces Formations are designed around much heavier firepower and expect access to even more when necessary. And for good reason, they usually get stuck with the worst jobs in the worst places.
Special Forces Company
HQ 1250
1 - 2 Forward Observer
80 Special Forces (Personal Weapon)
16 Special Forces Weapons Team (Mix)
16 Armed Transport (Mix of anti personnel, anti vehicle, anti air and autocannon)
Yes, Special Forces get Forward Observers at the lowest level that can be depicted in Aurora.
Special Forces Battalion
HQ 5000
4-8 Forward Observer
240 - 320 Special Forces (Personal Weapon)
48 - 64 Special Forces Weapons Team
48 - 64 Armed Transport
Attached Artillery Battery (4-12 guns)