Depends on the size, I guess. But SLDF "Combat Commands" would most likely be what they called "Divisions", which were essentially multi-regimental formations:
- 1 Regiment of "Tanks" (Armor or CV)
- 1 "Artillery" regiment (either a regiment of things like the Long Tom Carrier or Padilla Arrow carriers, or towed field guns/artillery)
- IIRC, either 1 or 2 Aerospace Wings (so 54-108 SF)
- "Infantry" Divisions would have 6 Infantry Regiments (either Motorized/Mechanized, Foot, or Jump) & 3 BattleMech Regiments (if paired with Jump Infantry Regiments, all of the 'Mechs had to have jump capability)
- "Mechanized" Divisions would have 3 Infantry Regiments (Motorized/Mechanized or Foot) & 6 BattleMech Regiments
Might have had more than that, but can't remember off the top of my head.
Plus, said BattleMech units were nowhere near as "mixed" as Succession Wars/Clan Invasion & later units are. The fluff talks about entire companies having only a single model of 'Mechs in them, or mentions certain types of lances that mixed only 2 types (i.e. "HK" lances with the Null Sig-equipped Spectors & Executioners, or the lances where they paired 3 of one type with the Talon for spotting). From a campaign perspective, basically instead of rolling for 4 different units per lance, you would only roll once for that lance.
Essentially, you ended with a formation that
technically had as many regiments as the later Davion/Steiner RCTs (9 Regiments in RCT vs. 12-13 SLDF), but even the SLDF Infantry Divisions were "'Mech-heavy" compared to IS/Clan formations (kind of like if you were to face
all of the DCMS Ghost Regiments in a single formation, or all of the Avalon Hussars). Clan equivalent would maybe be a Galaxy...but the Clanners would be light on the Infantry/Elementals side.