This is my third attempt to come up with a countermeasures-based defensive layer as an alternative to the point-defense system currently in vanilla Stellaris (and if nothing else it's much less wordy than before). The primary mechanism is the use of utility slots to supply decoys and jamming emitters that interfere with the effective accuracy of direct-fire (DF) and missile weapons. Each utility slot provides a certain amount of effective damage capacity, similar to shields or armor, with the following differences:
Smaller/faster weapons become a bigger threat to larger ships as they quickly strip CM capability with their rapid attacks. Strike craft don’t add too much here, in part because their attacks aren’t as likely to be interfered with, although their very low cooldown keeps them effective. Larger/slower weapons will probably have some difficulty getting unanswered one-shots on smaller ships, with the possibility of nullifying a single big hit.
I don’t know if I would want to see auxiliary slots for larger ships that alter the behavior of CM utility slots, by shifting the chance to be affected away from smaller attacks and toward larger attacks, or for hangars that cause their (offensive) SC to be more effective at stripping CM (either by chance or multiplier). But it could be a useful trade-off versus other aux modules.
- Each attack has a percentage chance of being interfered with by the countermeasures (CM). It would likely default to somewhere between 25% and 50% for Tier 1 sensors and Tier 1 CM modules. Units without explicit sensor modules (e.g., space whales) would have a set rating for each type; I don’t know if non-technological units would have CM-type capability or how that would work.
- Smaller (e.g., S-slot) weapons have a small (5-10%) increase in the chance to be interfered with by CM, while larger (e.g., L-slot, X-slot) have a similarly lower chance to be interfered with by the same CM. Missiles have a significantly larger chance increase than a same-slot DF weapon (more reliant on their internal sensors, although Torpedoes might be less affected), and strike craft have similar chances to other L-slot weapons (due to their point-blank attacks).
- As CM technology improves and is refit into warships, the higher Tier modules apply a larger chance; similarly, sensor technology improvements apply a reduction in the chance to interfere. Missiles see this type of improvement based on their own improvement more than for the sensors themselves.
- Any attack that is subject to CM interference applies its full damage to the CM layer (times any damage multiplier), not to any later defensive layer (i.e., what would have been a hit is now a miss). Fast cooldown weapons have a bonus to the amount of damage they apply to the CM layer, while slower cooldown weapons have penalties to their damage applied.
- Once the CM layer is defeated, it stays down until after combat or a set amount of time after last having been hit while still in combat. I don't know if I'd apply any modifiers to the chance to interfere based on the ratio between the incoming damage and the remaining CM capacity, but it's something I might consider.
Smaller/faster weapons become a bigger threat to larger ships as they quickly strip CM capability with their rapid attacks. Strike craft don’t add too much here, in part because their attacks aren’t as likely to be interfered with, although their very low cooldown keeps them effective. Larger/slower weapons will probably have some difficulty getting unanswered one-shots on smaller ships, with the possibility of nullifying a single big hit.
I don’t know if I would want to see auxiliary slots for larger ships that alter the behavior of CM utility slots, by shifting the chance to be affected away from smaller attacks and toward larger attacks, or for hangars that cause their (offensive) SC to be more effective at stripping CM (either by chance or multiplier). But it could be a useful trade-off versus other aux modules.