New feature: Void Veil

[Oberlus]

I've just finished reading certain trilogy of sci-fi (trying to not spoil, so I won't say the name) full of interesting ideas.
One is what I'll call here (to not use the same terms used in the novel) Void (or Black) Veil: an area of space where speed of light has been nerfed to a speed smaller than the scape velocity for that area (which makes sense only under gravity wells such as a star system).
In the novel that creates a barrier that won't let light (nor anything else, since light speed can't be exceeded) scape the gravity of the system, effectively making the system work as a black hole without destroying what is inside of it.
FreeOrion already has something with a similar, or even equivalent effect, the Gateway to the Void, that effectively destroys the system and any ship that dares to stop by it.
Here I'm thinking of something different: make the system invisible (hidden) except for ships within it, regardless of the detection level, and greatly reduce speed of anything in the system (or passing by it?). So an Empire would have vision of its "blackened" systems, but any enemy would need to send scouts or anything else there to get vision. In practice, that would mean increasing stealth level of anything in the system to a level greater than the maximum detection level, and the speed reduction... would be great if it could be something like -90%, but I don't know if that is possible.

Do you like the idea?

[Ophiuchus]

The veil from the novel does not have any value for an empire but as an trap for enemies. No information or matter can get out so no RP or PP or Defense or Ships from that system. If you like to keep the spirit it could become a Void Veil Trap.

Planets in the system get their own supply group, no export to imperial stockpile (import could be ok) and export of RP (new techs are ok, as import of information is possible). Actually supply import would also be ok.

No ship or planet can leave that system (maybe passing also traps the ships?).

You can break the trap by removing the trap building(?). So an enemy can break the trap by invading the planet with the void trap.

I think this could be interesting. Implementation wise

• easy: no RP contribution (simply set it to zero on all planets in that system)
• easy: no ships can leave (zero fuel for all ships in that system)
• probably easy: trap slow ships trying to pass (zero fuel for the ships on starlanes on the way, change target for ships which are on starlanes away from the system)
• problably not too hard: trapping fast ships which try to pass - even if they can completely hop in and out of the system in a single turn. We can ensure a stop by some kind of blockade via some "monster" unaffected by the Void Trap. Monster is active, has very high stealth and detection and does no damage.
• hard: own system supply group - the monster could block supply propagation but the planets would be disconnected from each other. Maybe we could add tags to the outgoing starlanes ("starlane terrain") like NO_SUPPLY_PROPAGATION and do without a monster. Probably not worth it, let each planet be isolated.
• very hard: supply only going inside - allow something like supply 0.5 which allows to connect inside the system, but not further and some notion of one-way supply. Maybe like a DrawPPFromSupplyGroup system = ID effect. Definitly needs reworking the production queue processing in server. Not worth it.

edit: If the fluff is not important; Concerning your suggested mechanic: A system hidden only from the outside seems like a corner case which will be especially hard on AI. This would also part of the local defense discussion (cost must be high so one does not build this everywhere)