Regarding the no-trade-across-orbit issue, if memory serves me correctly, the reason I set it up like that is because I wanted to force extraterrestrial cities to produce their own resources. Initially, certain buildings on Mars would produce the same bonuses as on Earth, such as Vegetables, before it occurred to me that I could create dedicated bonuses like Martian Vegetables. In other words, the original rationale for this design decision no longer applies and I think it could be safely changed if desired.
So I could these tags on techs as gates.
Code:
<TerrainTrades>
<TerrainTrade>
<TerrainType>TERRAIN_OCEAN</TerrainType>
<bTerrainTrade>1</bTerrainTrade>
</TerrainTrade>
<TerrainTrade>
<TerrainType>TERRAIN_OCEAN_POLAR</TerrainType>
<bTerrainTrade>1</bTerrainTrade>
</TerrainTrade>
<TerrainTrade>
<TerrainType>TERRAIN_OCEAN_TROPICAL</TerrainType>
<bTerrainTrade>1</bTerrainTrade>
</TerrainTrade>
<TerrainTrade>
<TerrainType>TERRAIN_TRENCH</TerrainType>
<bTerrainTrade>1</bTerrainTrade>
</TerrainTrade>
<TerrainTrade>
<TerrainType>TERRAIN_TRENCH_POLAR</TerrainType>
<bTerrainTrade>1</bTerrainTrade>
</TerrainTrade>
<TerrainTrade>
<TerrainType>TERRAIN_TRENCH_TROPICAL</TerrainType>
<bTerrainTrade>1</bTerrainTrade>
</TerrainTrade>
</TerrainTrades>
Space surrounding objects would act as sea
That is Orbit, Cislunar Space and so on.
Sea of space stops being a thing at Orion Arm zone.
Still they can cut entire map across.
I'll test that if tech gating would work at first place - build tunnel connecting pair of cities trough ocean.
While trade route icons appeared, there is no sign in city, that they are connected (there would be trade with other city).
Barley appeared in city across ocean, so it seems you can't gate space zones with techs...
That is <bTerrainTrade>1</bTerrainTrade> just allows trade without routes, and you can't build routes on water tiles until you get tunnels at end of Industrial era.
So this would depend on techs, that unlock space routes instead.
Solar Worker can build Solar Trajectory, that unit and route build are unlocked at TECH_ASTROGATION_CONSTELLATION.
Currently it has no Cislunar mapcategory, Orbit and Cislunar Space have this mapcategory.
So I need to add <bCanMoveImpassable>1</bCanMoveImpassable> and Cislunar mapcategory, then you can connect Earth to space colonies at TECH_ASTROGATION_CONSTELLATION.
This tech is somewhere in Transhuman era, so you are already expanding in outer solar system.
On Earth side you can build tunnels or land routes to connect to space.