Now that we can design ground formations, I'll dork out a bit in practice, not just in theory.
Here are the basic formations I've made so far. I've designed most of it around 10k ton sizes, because that's both a reasonable number at first glance, and it's the size of my standard transport.
I've got a couple levels of defensive units. These are basic but all-around units, trying to keep cost down while still allowing them to be functional military units against most plausible threats.
Garrison Regiment
Transport Size: 9 971 tons
Build Cost: 320.2 BP
1440x Infantry (INF, PW)
48x Machine Gunner (INF, CAP)
24x Stinger AA (INF, LAA)
24x Bazooka AV (INF, LAV)
20x Small Logistics (INF, LOG-S)
2x Hephaestus Construction Vehicle (VEH, 2xCON)
1x Thor Orbital Defence Outpost (STA, 15cm C3 Near UV Laser)
1x Zeus Regimental Command Vehicle (VEH, HQ10k+FFD)
Garrison Division
Transport Size: 9 962 tons
Build Cost: 878.8 BP
420x Infantry (INF, PW)
24x Passchendaele Artillery Installation (STA, MB)
24x Pillbox Anti-Tank Installation (STA, MAV)
24x Hawk Heavy AA Installation (STA, HAA)
12x Logistics Truck (LVH, LOG)
4x Thor Orbital Defence Outpost (STA, 15cm C3 Near UV Laser)
4x Hephaestus Construction Vehicle (VEH, 2xCON)
1x Cronus Divisional Command Vehicle (HVH, HQ50k+FFD)
This is designed to command four regiments, and add in some heavier firepower to support them. Infantry are mostly to guard the heavies if it gets attacked, and to bulk it out at a low cost. It's actually kind of shocking how much of the cost of these is the orbital defence weapons - the four Thors are almost half the cost of the formation(382.7 BP), and they don't even have the top-tier armour for static installations. I would probably prefer to add some smaller weapons for anti-missile work, but STO weapons are sufficiently expensive to design that I only have one in service so far.
I also might add a bit more in the way of construction vehicles. I don't have any division formations actually built yet, but I have a regiment that's been entrenching for a few years, and at this rate it won't hit max until like 20 years in. (The infantry are at 4.28 fortification level, and nothing else is above base). The division won't be helping much in practice either, since it's light on them too.
These, conversely, are offensive units:
Tank Regiment
Transport Size: 9 848 tons
Build Cost: 799.8 BP
108x Ares III Main Battle Tank (VEH, MAV+CAP)
24x Hera Support Tank (VEH, HAA+MAC)
1x Zeus Regimental Command Vehicle(VEH, HQ10k+FFD)
Tank Division
Transport Size: 9 910 tons
Build Cost: 514.1 BP
48x Normandy Medium Artillery (LVH, MB)
12x Watchman Heavy AA (VEH, 2xHAA)
10x Hephaestus Construction Vehicle (VEH, 2xCON)
36x Logistics Truck (LVH, LOG)
1x Cronus Divisional Command Vehicle (HVH, HQ50k+FFD)
The lack of organic supply in the regiments means I need more at the division (14,256 total supply for the formation, and I can supply 18k here), and by the same token some ability to dig in could be helpful. Likewise, artillery should be behind the front line, and an offensive unit shouldn't need STO coverage. I added a bit of AA for redundancy, but TBH the 96 guns in the rest of the division is probably more than enough against any plausible division-sized garrison. If I keep this division design, I should look at re-designing the Hera a bit, I think - drop the HAA to LAA, and up the number from 24 to 36. Ah well, this is why we iterate.
Finally, I'll be equipping my cruisers with an anti-boarding force:
Marine Company
Transport Size: 200 tons
Build Cost: 10.7 BP
38x Marines (INF, PW, Boarding trained)
1x Battalion Command Post (INF, HQ2k)
---
Overall, the thing that makes this feel very different from my pre-launch theorycrafting is that units need to be researched. I don't have all the various bells and whistles, I don't have the ability to tailor elements perfectly (unless I'm willing to waste a ton of RP on doing so), so I need to make things fit. It's a different dynamic, especially in the early game when tech is advancing really fast. But I'm enjoying it, for sure.
