I've read through the above posts and I will give STO vs CIWS more thought.
My original thinking for excluding turret-based weapons on planets was the intended 'static' STOs would be well-fortified and therefore not ideal for tracking fast targets such as missiles. Turrets would need room to 'manoeuvre' and therefore didn't match the well-fortified concept. CIWS on the other hand were very short-range and intended to hit targets coming directly at them.
Another reason for not having turrets was that I didn't necessarily want planets to have defences that were so strong you couldn't penetrate them, because those turrets would be as effective as orbital bases but much harder to kill.
However, some good arguments have been made against those concepts. Firstly, CIWS in this context are effectively covering the whole planet, which doesn't really match the CIWS on ships. Secondly, the new STO units are really the same type of integrated weapon as CIWS, making CIWS less 'special' in this context. It probably does make more sense (and is more consistent) to remove planetary CIWS and allow STO to include fast tracking weapons, as CIWS is really just an integrated gauss turret anyway. This also makes it clear that planetary defences can protect ships that are in orbit or close to the planet. If I made this change, I would add point defence modes to the other automated options for STOs, which would also mean that 'normal' STO could be used for point defence in an emergency.
The 'downside' is that some planets/bases may become very hard to defeat, although that is not necessarily a bad thing. It also restricts the potential use of small, fast craft for dropping troops and the best option is probably large, heavily-armoured assault ships. Again, not necessarily a bad thing.
I think I decided early on to go with non-turreted STO plus CIWS and then stayed on that track. At this point I am just stepping back and questioning my own assumptions
hmm... not sure..
I understand the point about CIWS being able to defend the whole planet - but that might me solved by saying that 1 CIWS is only able to "defend" only the area of a planet it can reach because of the curvature of the planet/body ...
let's say a CIWS mounted on the highest mountain/hill in the region has a "field of view" of 10-25% of the Body max ...
which would lead to a 10-25% chance for a CIWS to get a shot.. the defender would have to build a lot of CIWS to make sure they can defend a planet without the planet being hit....
which would make sense... the defender in ground-air-combat is in RL at a disadvantage every time.. the attacker can mass his attack at 1 point while the defender has to defend the whole area...
not every German FLAK all over the Reich was shooting at incoming bombers - only these in range...
for turret based STO units... I am afraid that this would be the end of "defence platforms" in space near a planet...
the main line of defence for a planet should be a mobile fleet, the second line of defence should be the defence bases in orbit and any ground based defence line should just be "last ressort" - not the main (and cheapest) solution to go...
there would be no point to build orbital defences at all if you could just build ground based ones which are cheaper (as without all the other things you need for a defence platform) and less easy to destroy themself... (we have this in VB6 as (nearly) nobody would build a orbital defence platform because the ground based "bunker" was the better/cheaper solution)
for me, planet based weapons should assist the orbital defence to some kind but that would be all... if the orbital defences are destroyed, the planet should be "doomed" - the army able to defend from an invasion but not to repulse an bombardment..
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if it is the main problem to make sure that "all weapons work same in orbit and on ground" - I cannot say I like this argument ... it is not wrong but thinking this through it would mean (for me) to just don't use the same weapons in ground units and add new weapon types for them instead...
nobody wants this so I am OK with the "same" weapons work differently... they are just "modified ground based types of the same principle"