So you're saying, alternative types of damage mitigation need to be more widespread, then. Rather than the common global 'take damage for you' force field being the only major thing.
Eh, I like variety, so I'd stand in agreement here. I also did have my home command sniped off by a single raid starship that my fleet was nowhere near enough to kill, so I'm mildly annoyed with 'immune to forcefield' being as awesome as it is... but that awesomeness does apply to me as well, so I don't really know.
...what this does make me want to do is come up with defensive beacons that apply a similar defensive effect... so, I'm going into a crazy fruitless brainstorming mode!
Armor Beacon: This similar-to-forcefield defensive structure will create a thin barrier around any structure it stands near. It will take 75% of the damage those structures would take instead, and cannot be ignored by anything that is immune to force fields. It also does not reduce the damage of ships beneath it, and does not protect ordinary ships from damage at all.
Decoy Beacon: If you give the Decoy Beacon a defensive target, it will act as a decoy for that target and that target alone, taking all of the damage specifically that target will take. Decoy Beacons cannot act as a decoy for anything with a weapon.
Point Defense Turret: This special turret acts as an attachment for a force field, and will, once every X seconds, shoot down an enemy attack that is inside of it, in an effort to hold off enemy raiders.
Cloak Field: This "force field" has next to no health, and instead defends things inside of it by turning them invisible. Structures inside of a Cloak Field cannot attack, and units cannot be cloaked by it. If the Cloak Field Generator is revealed by tachyon beams, so is everything underneath it. (Couple this with the AI possibly putting forth more effort into decloaking things)
...This was largely unfocused but maybe there are some discussable ideas in there that someone wouldn't mind polishing up?