Yes, I know Ground Combat has been the orphaned left handed step child who was hidden under the closet since birth in Starfire...but the RM is planning to take over an alien race and I'd kind of like to brainstorm a bit consider this a bit of stream of consiousness thinking on my part over this topic.
1. Kinetic Interdictors and Ground Support Fire...
The rules for KI's are vastly odd. While it is possible using missiles from ships to obliterate a worlds PCFs in under 5 min (this is something that you would classify under "WW1 Artillery General's wet dream") Kinetic Interceptors are first of all governed by a extremely random die roll (1-100% effectiveness), are exceptionally expensive 6MCr per 3 CFs, and can only do 50% damage to the enemy. Their cost is mitigated somewhat when you consider they have no maintenance and 3 CFs is a not bad amount given how many PCFs you could potentially kill. But you have to question if spending 24,000 MCr on a system (as the example in ISW4 tech gives) would not have been better spent just buying more PCF-x's. Also a bomb that can kill a PCf costs 0.01 MCr...so why on earth are these things which are no where near effective and are 7 Tech levels higher so ungodly expensive? If memory serves 1 nuke kills one PCF in the SM2 changes to the planetary bombardment table.
In imperial starfire it is stated that you can decide to fire non-nuclear weapons in defence of a PDC under ground assault so I will assume that you can do so for orbital bombardment or shuttle dropped bombs. The trouble is that how do you apply this CF? Looking at the rules you would have to do the same as for the KI's and also make the limitation that you could only kill 50% of the defenders (include all other rules as well about spotters etc...there is no way the KI's are worse then a missile in terms of guidance since they require a ships fire control to be used anyway). This would mean that for each non-nuclear warhead or shuttle dropped bomb used you would get 1 CF. A CA with 6 Wa could then fire 60x2x6x1CF= 720 CF worth of missiles in an interception turn for a cost of 72 MCr. The equivellent in KI would cost 1440 MCr. Pardon me but this is absurd. A ast could drop 60x2x1CF = 120 CF in bombs for 1.2 MCr while that would cost 240 MCr in KI. Even factor in the cost of the ast and you are at 31.2 to 240 MCr.
So add that to the pool from KI and make a roll. Personally I would be more inclinded to make this a guassian roll (2d10 and look up a result on a chart) so it can be bell curved since ground combat isn't so wildly divergent...
But again the cost of the KI comes back...why is it so ungodly expensive when you consider that a SM costs 0.1 MCr and does 1 CF (according to the rules all non-nuclear warheads to 1 CF). That says to me the KI should cost about 0.03 MCr to 0.3 MCr each...it can't be more expensive then 3 Ground attack SMs, which after all are full sized missiles not a mass driver and kinetic kill projectile. Split the difference and say 0.2 MCr per KI. Is that too cheap? The real point I think is that you can buy a PCF for 6 MCr that is going to give you more than 3 CF and fires more than once even if you have to pay maintenance. If you use the example from ISW4 technology you would be much better off taking your 24,000 MCr and buying 4,000 MCr in ground troops and using the other 20,000 MCr for maintenance on them then wasting your time with 24,000 MCr worth of KIs. 300 more PCF-12a's would have added a lot more chance that they would win the battle then landing 200 troops supported by 24,000 MCr in KIs. Either that or land only a single spotter per planetary area, and cut the enemy down by half each attack. Done 2 times (by which time you should be out of KIs) would have cost the attacker 12 PCFs. The enemy would have lost a good fraction of their troops (between 50-75% in each combat area)...2 attacks in each planetary area with around 1000 CF of KI's.
2. Detecting and destroying PCFs
Anyone who has ever seen the rules from Traveller spots very quickly that some of the first systems routinely adopted by militaries are stealth suits and chaemloen battledress and advanced armours. This is what is happening now, so let us assume in the future in Starfire they don't line up in parade formation in open ground why don't we? Modern militaries are far more resistant to nuclear attacks then civilian infrastructure. They would include intergal ground to orbit defence and attack systems so "nuking them from orbit" should be a more difficult proposition then just firing a random missile at them. They know about the ships in orbit and can track them easily enough to avoid them (terrain is a factor). The ISW4 bughouse scenario again doesn't make sense...how could the TFNs troops have hidden? How could they have hidden the people? How could they have moved the people under the observation of the bug orbital weapons platforms? Typically what White/Webber writes in the books is at extreme varience with the starfire rules but that particular part was baffleing...also the KI's used in those battles seemed to be far more effective then the ones in the rules as they destroyed several bug columns on the move.
Anyway personally spotting PCFs from orbit should be a tougher proposition...they don't launch flare guns afterall. And then killing them should be TL dependent and they should have intergal point defences as a function of tech level of the PCF. But as things stand you are in a vicious circle...PCF's are worthless because you can just nuke em from orbit, you can nuke em from orbit because the rules make that a trivial inexpensive task therefore PCFs are worthless...
3. Shuttle Air Support
The thing is that the ast doesn't have a point defence suite. It has ground attack weapons which can be used to defend the shuttle and to attack other small craft. The pn has heavier versions of these same weapons but again doesn't mount a point defence suite. So why is the damn ast or pn not given an explicit ground attack value. From Imperial Starfire point defences are worth 1 CF. So an ast or pn is worth 1 CF in terms of ground support. But they can drop 2 bombs ever 30s so in 60 rounds so in a 30 min interception turn they could drop 120 bombs each. For, again ignoring nuclear options, an additional 120 CF. That is 0.25 MCr per CF looking at the price of an ast only ignoring the basic 1 CF the ships "ground attack weapons" give it and the cost of the bombs (1.2 MCr) . Also ISW4 talks about shuttle mounted KI's which are not in the rules.
It would make far more sense to me if the CF from a shuttle (basic ground support) increased every (as a guess) 3 levels TL3 CF1, TL6 CF2 or TL6 with KI developed CF4, TL9 CF3 or CF5 with KI developed, and so on.
It would also lead to lots of destroyed shuttles if ground units had an inherent point defence ability...no matter how low the chance was with 100+ PCFs your shuttles (of which there is unlikely to be more than 40 or 50 in most cases) would end up dead long before they dropped too many troops.
4. "Low" Level Guerrilla War
This is anything but low level 2-20% of the planets garrison and GPV reduced each month? That means in general in 10 months on average the planet generates no income. Uhm...this is someones wet dream but lets be realistic here. Partisan forces can't survive contact with regular military forces. Partisan forces without support last very very short time frames. Without a safe haven an insurgency is pretty much doomed. So how about .2-2%? Also these things are impossible to stop in starfire...or I missed the rule for how one ends one outside of a political offer. How about every turn you don't reduce the garisson below minimum your LLGW militancy goes down by 2% and a further check against the new LLGW militancy is made to see if the movement peters out is made? Because honestly under the rules in starfire if one starts you would be better off to reduce your garrison to trigger a general uprising and then crush it then to fart around trying to deal with the LLGW. Crushing a general uprising also dramatically reduces militancy if memory serves. I find it astounding that regular military forces can be blotted out of existance in mere minutes by a few orbiting corvetes yet freedom fighters are able to kill 20-30 PCFs per month without being spotted, tracked and destroyed (given the total control of the orbitals the occupier has).
5. Losses
The time scale of ground combat is that in 30 min so worst case the battle for the planet could be over in 30 min...hard to see how it might take even 1 day. This is absurdly short. Also why is everyone dead? Modern combat doesn't kill everyone in a combat unit...heck 10% casaulties of an entire combat formation are very heavy for an attack (10% of a units full strength is considerably higher fraction of its combat sub units). So losses should be split between disabled, dead, and captured. At a guess 50%, 20%, and 30%. Every day 1-6% of the disabled should return to duty (roll a d6) representing light injuries, and the fact some of that is just disrupted formations that make it back in drips and drabs later. As it is...it is like that original star trek episode with the two planets at war and the booths...
I'll have to look at what Galactic Starfire has...maybe there was some improvements. But the rules in Imperial Starfire and the SM2 updates...blah... Nuke everything from orbit it is the only way to write rules seems to be the watch word.
added in edit: combat is one roll per 30 min interception turn, and that is 60 tactical rounds...this makes missiles even more effective. A couple of CTs with 2 W and 2 Mg would be able to destroy 60x2x2=240 PCF's per interception turn for a cost in ships of 400-500 MCr, in total (400 missiles per ship) they could destroy 800 PCFs causing a total of 80 PU/IU losses to the world. Actually they may do x2 of that as I think it says 2 PCF per EVM. The best you could do with KI (lets assume there are 800 PCFs on the world) is 400...lets say they are PCF-6 (8 CF per PCF) would require on a 50% roll: 2133 KI or 12798 MCr plus shipping (86 H required). That kind of cash is over 100 turns of maintence on the CTs...
I just can't see how they (whoever it was that did so) came up with the cost of the KI system...