So I know I was leaving this up to Horizon, but I changed my mind, and feel that we can help make community decisions,
Anyways the general idea is that Mines/Orbital Weapons platforms are the best thing to take for defenses.
So here we will discuss (and my first takes on every one)
Orbital Defense Platforms: These are somewhat internally unbalanced, I reccomend that the weapons platform go down to 45cm weapons batteries, and possibly the torpedo launcher go to 4 torps (maybe 5)
Mines/Minefields: Perhaps increasing the cost of mines to 10 points, or making them 'die' to turret fire (if the turrets get two successful hits) Although this may mean revising the mine launcher variants of ships? Minefields probably an increase to 60-80 points.
Fireship: Seems fine
System ships: Decrease in cost to 15? Or increase of speed to 20?
Monitor: Decrease to 55? Maybe just leave alone.
Orbital Dock: Seems fine, although I could see its armor go to 6+ as 6+ armor on defenses =~5+ armor on capital ships (it's a little better but not significantly)
Space Station: I want to see this represent the model, so I'd ditch the launch bays, up its armor to 6+ (as this seems necessary for defenses) and probably make it cost 100-130 points.
BSF: This should have a line... can be used to represent any large space station. Also probably should have 6+ armor as well, but that would make it cost around 500 points I imagine.
Activated BSF: this thing is somewhat crappy compared to the standard BSF, I'd make it cost similar to the BSF or give it turrets. (say they are some high energy power arcs that destroy nearby small craft). It always gets destroyed by bombers as it has no turrets.
Laser, Missile & Air Base ground defenses: Seem fine
Ramilies: Needs to be balanced with the Fortress Monastery, either it needs 6+ armor (which I think makes sense for all defenses), and a cost increase of ~90 points, or it needs to be cheaper.
Xenos Varieties:
Tau Orbitals: Probably Ok, but could use 6+ armor. Maybe an increase in the value of habitat modules (2hits for +10 points instead of +1 for 5 points)
Other Tau things (security orbitals/city) Do these need anything?
Eldar: Does anyone think that the base needs changes?
Orks: In my 'Ork flawed ships' I made different Rok variants, and these seem ok. The better leadership seems to counter with them being immobile. Also I added in 'MAD' Roks which cost 40 points, have no weapons, can only be taken as defenses and have the fireship rules.
Current lists for what is available to various races for defenses:
IN/Chaos:
Fireship
System Ship
Ramilies
Orbital weapons
Mines & Minefields
Space Station
Orbital Dock
BSF
SDM
ABSF (chaos only)
Ground Based Weapons
Orks:
Roks
Orbital Weapons
Mines & Minefields
Space Stations
Orbital Docks
BSF
SDM
Ground based weapons
Fireship
System Ship
Hulk (as a defense for pirate bases)
Tau:
Orbitals
Security orbital
Orbital City
Ground defenses?
Eldar & DE
Haven
Necrons, Nids:
None
I think that Orks should use 'Ork Ordinance' when they buy vessels with launch bays. I'm pretty sure they would be the only ones who would put assault boats on a space station....
Also Eldar & DE could see some more options for defenses. Necrons and Nids could see some in general, I know its kind of unfluffy for them to build them. However Nids could easily use most of the IN/Chaos ships and just 'say' that they are their biological equialents. Similarly they should use Nid ordinance. Necrons could just receive more vessels (I.E. they could spend their defense points on escorts, but probably not a capital ship)
There should be a standard for what people use as a pirate base in campaigns. I would reccomend a BSF. However Eldar would get 2 havens? Maybe if there was a larger option or some similar thing.