In my view it is erroneous to think of the CON component as combat engineering units, it is specialized as TN heavy construction equipment and really does not work in the way that battlefield engineers do, this much is apparent from their actual game mechanics (fortification, ruins recovery, and factory production - all very much heavy construction tasks, not battlefield engineering). Much like recon or signals assets (aside from FFD) engineers are not really modeled in Aurora which is an unfortunate limitation of the GC system.
It is worth noting though that the CON elements, and in fact I believe all of the ground unit techs except for troop transports (why?!) and power armor can be developed without researching TN tech. I think of it therefore as developing the tech for developing TNE-enabled construction units (even in conventional starts, a race still uses TNEs for its conventional industry after all) which are able to carry out spaceborne operations. It's not like the race has forgotten how to build bulldozers and dump trucks, but in the new interstellar era some new technology is required nevertheless.
Okay. So that means CON units are basically mobile heavy construction factories.
Why do these units require some TN developments, in order to become a thing - we already have conventional factories, which are more versatile than the later specialized variants (ironically) - what, they can't design a fatboy (from supreme commander game) mobile factory? They MUST have TN technology?
The same goes for troop transports...
As I said in my previous post, CON can be researched and developed without any TN tech...it is a "conventional" (or pre-TN, you use whatever words you like) technology but it still has to be developed. If I am developing a conventional setting I have no problem SMing in the tech for RP reasons, same with things like heavy armor or HCAP, there is no reason a pre-TN society could not develop those toys but it still takes some research to do it unless you RP that the technology is already known. Given that even in the 21st century we do not exactly have 300-ton construction vehicles which are
space-capable and can operate not just on Earth but on the surfaces of the Moon, Mars, asteroids... I don't think it is unreasonable to have to develop the tech at least in some settings. Aurora is at its best when we can RP however we want and I think the current setup makes this very possible IMO.
Defining things as "conventional" versus "pre-TN" is up to the player IMO. Yes the conventional/pre-TN units do cost TNEs but this is a limit of the game and one I am perfectly happy to fluff away if my setting calls for it.
Troop transports will have a conventional/pre-TN variant in v2.0, and I for one look forward to this eagerly.
So, I'm starting the 3rd iteration by dropping all Pen. and Dam. values down considerably for every GC weapon at all, so that ground combat must became several times longer. It's obviously not the absolutely best option, I think nearly anyone wants the opposite, yet I really, really want CSAPs and arty to be the best damage dealers in the case of massive LOG support ONLY. There might be some border issue with conventional zero-rounded Pen., yet it's bearable for me personally, because I use conventional techs only for making a "pre-game" set of weapons to give my troops some sort of historical roots.
I have been working on my own somewhat less dramatic set of ground combat adjustments... I think I will soon be writing them up into a "mini" AAR so I won't get into extreme detail here.
For scaling of GSP requirements I have introduced two rules. One is to increase scaling with the #shots to the 3/2 power (roughly, I do adjust numbers to look neater in the final version) instead of linear scaling as currently. This makes CAP/HCAP, bombardment, and autocannons all cost more to supply, particularly CAP and MAV have similar GSP demands which makes medium tanks not as sub-optimal anymore. Second rule is adding a multiplier based on bombardment statistic (BBT) for both GSP and tonnage/size stats. GSP is multiplied by (1.0 + 0.5 * BBT) and size very approximately by (1.0 + 0.25 * BBT). This makes artillery units both cost more (GSP
and BP costs) and require more transport space as an added cost to the long-range bombardment ability (BBT = 1 for LB, 2 for MB, 3 for MBL/HB) which is not really accounted for at all in the vanilla modeling.
In general my changes are not as "extreme", but bring CAP and artillery into better balance with AV and AC weapons and I've been fairly happy with the results in theorycrafting exercises. Generally my line formations require ~10-15% tonnage in LOG modules to fight for 10-14 days, and my artillery requires about ~25-33% for the same, with higher echelon LVH+LOG vehicles requirement being quite demanding beyond ~1 month of sustainment (this is even with the large LOG modules providing 1,000 GPS instead of 500!). It feels a very good balance but playtesting will reveal how it really is.
I mention this to suggest that compared to the changes listed in the thread, reducing the lethality of CAP and artillery (mainly in terms of #shots, which is after all an abstraction) while keeping the heavy supply demands may be the way to go to achieve the style of game you desire.
I am also glad not to be the only one who insists on a large pre-TN force for the sake of realism.
That said I do not think there is a "border" issue with penetration as the ground combat mechanics seem to be set up to permit non-integer values.