Sensor relays, if implemented as proposed here, would be objects that can be placed in nodes by players (except for the Unfallen) to provide map vision, beneficial Theater Effects in space combat, and - with upgrades - other benefits for your empire, its allies, and its minor faction vassals.  These features of relays would provide players with more rewards for peaceful/cooperative gameplay and cultivating relations with minor factions, and would give pirates more targets to mess with.



Placement


Relays would be placeable by exploration ships (equipped with the appropriate module) in special nodes and star systems that are uninhabited, have outposts, or are colonized by yourself or an ally/vassal.  Similar to placing Unfallen vines, placing relays would require a 5-turn wait - but would also cost some Dust (or influence for the United Empire).


Multiple players can have relays in the same node as long as it isn’t colonized by someone other than an ally or vassal.  However, this doesn't mean other players won't try to keep the node to themselves by destroying your relays (see "Behavior" below).



Behavior


In order to function, relays would need to be ‘linked’ to at least one relay in a colonized system (owned by the player) by other relays in adjacent nodes connected by starlanes.


Visually, relays would appear as wireframe objects orbiting the outer edge of the system, like Vodyani Arks.  Relay linkages between nodes could be visually represented by replacing the normal white shimmer of starlanes with a shimmer of the color of the empire that owns the relays (see rough visual below - wireframe relay models not depicted).



When an undefended system or node with a relay is attacked by enemy ships or pirates, the relay would be destroyed in a way similar to how civilian ships are plundered.  Destroying a relay would yield a small Dust reward and disable the remaining relay chain if it is no longer connected to a relay in a colonized system.  If disabled relays are hidden by the fog of war, the player won’t receive a notification if they’ve been destroyed.


Destroying an AI player’s relays would anger them unless you use privateers, providing more uses for this feature.


Having a Shared Vision treaty with another empire would allow them to benefit from your relays’ vision and space combat buffs.  Like Unfallen vines, having a relay in a system owned by an allied empire or a vassal minor faction would give them FIDSI benefits (see "Tiers" below), and the relay’s owner would also receive a cut (~20%?).  The player would also benefit from other friendly empires’ relays in the same way.  Thus relays would give players more rewards for peaceful gameplay or Vodyani-style cultivation of vassals, and more ways to help out their allies.



Tiers


Similar to planetary specializations, relays could come in upgradeable tiers with advancing empire and theater effects, such as:


Relay Mark I (“entry-level model”)

Unlocked by:  Baryonic Shielding (Tier 2)

+1 Vision Range on system

+1% Critical hit chance on friendly fleet

+5% Ship Evasion on friendly fleet

Cannot connect through wormholes


Relay Mark II (“second gen upgrade”)

Unlocked by:  Wave Function Control (Tier 3)

+2 Vision Range on system

+2% Critical hit chance on friendly fleet

+8% Ship Evasion on friendly fleet

+2 Science per turn on empire (+3 or +4 for special nodes, stacks with benefits from having in influence zone)

Can connect through wormholes


Relay Mark III (“military tech put to civilian use”)

(Only in colonized systems - relays in uncolonized systems would remain Mark II)

Unlocked by:  SLC (Supra-Light Content) Systems  (Tier 4)

+2 Vision Range on system

+2% Critical hit chance on friendly fleet

+8% Ship Evasion on friendly fleet

+2 Science per turn on empire

+0.25 Influence per pop on system

+0.25 Happiness per pop on system


Relay Mark IV (“new uses for old infrastructure”)

(Only in colonized systems with Distributed Energy system improvement)

Unlocked by:  Exa-Volt Beam Focus (Tier 5)

+2 Vision Range on system

+2% Critical hit chance on friendly fleet

+8% Ship Evasion on friendly fleet

+2 Science per turn on empire

+0.25 Influence per pop on system

+0.25 Happiness per pop on system

+4% FIDSI on system



Misc


To give players more of an incentive to build (and protect) sprawling sensor relay networks, perhaps empire bonuses could scale with the number of relays, as the network’s value grows along with its interconnectedness.  To limit relay spamming, however, the Dust/Influence cost of placing relays would increase as the number of relays (and thus bandwidth demands) owned by an empire increases.


To make relays useful as espionage tools (and to make probes useful as late-game counter-espionage tools), a tech advancement (Deniable Operations?) could render an empire’s relays invisible within the borders of its enemies except to probes above a certain Expedition Power.


Quests could also center around relays, with mysterious events occurring near or affecting/disabling relays in remote, uninhabited nodes.  Also, an extended ENFER quest line could involve ENFER hijacking relays to expand its control over multiple systems.