it could work like class missile loadouts: formations have priority ratings like ships do, the system checks formations by priority ratings, fills them up with missing equipment til it hits their rated size and then swaps out the most common vehicle with the highest xp in the formation that's not in the template and replace it with the least common vehicle that is for as long as it has a supply of vehicles that should be in the formation's template. I believe that should work without requiring vehicles to be assigned a 'series' or requiring the game to assume that two vehicles with equivalent configurations but different tech are in the same series. Elements could also be assigned priorities so that cadres tend to gravitate towards the best available equpment, perhaps with the caveat that infantry has to stay infantry.
I am not sure how lethal combat is but given the timeframes involved in a combat round it seems like it'll be less WW2 and more Battle of Hoth. Wars will be relatively short and incredibly violent. I dont know how much time there is for a formation to adapt, loot, reconfigure, etc. in that environment. Fortunately it also means that logistics are not a real concern.
///////
It just struck me that dropship design is under question since now ground unit size is highly variable. Combat drop bay size will have to be modular or players will design to breakpoints. Went and looked up real life equivalents out of curiousity:
the C-130 transport plane has an empty weight of 33 tons and can seat 64 paratroopers/72 combat troops or 2 APCs. Call that 64 guardsmen, or 2 hellhounds. In terms of Aurora that would work out to 320 space, or 84. It would take ~13 c-130s to transport a Guard Regiment using the infantry approximation, or 47 using the hellhound approximation. This works out to 430 tons of c-130 or 1551 tons of c-130 using the the respective approximations. If you prefer to use the full weight of the aircraft for the tonnage equivalent, you about double the aircraft tonnage used.
an alternative figure might be based off the LCAC, a beach landing hovercraft used by the US navy. This is not as similar to a spacecraft, but is a more military craft designed with more expectation of being shot at. It's (as best as I can find) 140 tons empty, and 200 tons full. It can carry 180 ground troops or 4 APCs of a similar weight as the c-130 or 1 heavy tank . The approximations work out to 900 space (infantry), 168 space (Hellhounds), or 104 space (Leman Russ). For carrying a Guard Regiment this equates to 5 LCACs (infantry), 24 LCACs (hellhound), or 39 LCACs (Leman Russ): 700, 3360, and 5460 tons respectively. The full weight version is about 40% heavier.
note that the above assumptions are based off 1 guardsmen in a regiment = 1 man. Since Aurora is arbitrary you could easily say 1 guardsmen = 1 guardsmen fire team, in which case the infantry figures could easily be 4-5 times as heavy when judging based off IRL equivalents.
also p.s. im not actually sure if Aurora warship tonnage are intended to be dry weight or full load weight..?