alright so here is another add on about defensive equipment. be aware though that these only reflect my opinion and experience or sometimes even just forum posts that seemed realistic.
add on armor:
this one is really straightforward, add it to a location and the armor will take the damage instead of the underlying equipment. note though that splash damage can and will still affect the underlying parts.
the best armor would obviously be one with high durability and high KE and CE defense. that doesn't exist (yet) though, so you will have to make a choice.
also when adding armor, adding armor in front of the cpit comes to your mind. you either need lots of spacers from sideway joints or you simply but the generator on top or beneath the cpit, and then use a diagonal spacer to the front of the cpit where you then add the armor plate. this also might have the benefit of make your cpit not so vulnerable to homing missiles as some forum posts suggest they go after the generator. that way the armor plate (depending on which one you choose) will cover most of the front view of the gen and the cpit, but probably not all of it. but still better than nothing. also this method doesn't work some cpits, as the diagonal spacer interfers with the cpit.
anti missile system:
these have a rating and set number of uses. you turn them on by selection it via left bumper and then activate them with the left trigger. however, if you switch to say thermo vision the ams will be turned off, so be careful. recent forum posts also suggest that adding multiple missile system will add the number of uses. some people suggest mounting it so that it faces to the side of your hound, however i didn't have any problem with mounting it facing forward on top of my gen like this.
ams
gen
cpit
also try to buy a higher rating ams from the shop or the lottery if you can, as the sp one is rather crappy.
radiators:
the oponions differ on this one, but i tend to believe the statement that they do absolutely nothing against missiles, cause i don't think they are coded to be "real" heat seeking missiles. however what they definately do is reduce your heat level, which in turn helps you against C ammo and incindary rounds. as you might notice, during a battle your heatlevel starts to rise while you fire and take hits, up to the point of reducing your effectivity. radiators help to counter this effect. also they decrease your visibility on thermal vision which should be obvious. but you can also overdo this, by supercooling your hound in a desert thus making you more visible again.
na jammers:
well, i think they are only useful against humans, and even then i am not absolutely sure of how they work. they DO hide you from the TCs radar/na maker, so you can sneak past them. i do not know if they also block enemy coms. the duration also seems to be increasable as well like the ams.
mines:
well, they kinda are defensive equipment. also straightforward. nice to have to block chokepoints to your base, especially against spikers, cause the will basically cripple their movement base straightaway.
smoke mortar (& thermo):
you can use the mortar with smoke grenades either offensively or as a defensive tool. useful for example to cover your quick getaway. if you want to use them like that, either mount the facing backwards or downwards.
on the offensive, use these in combination with thermo in close quarter battles and hope your enemy doesn't have thermo as well. be careful though, you can't tell in thermo when the smoke wears off.
so what? i could care less about the human race...