Multi-Island Colonies and Inter-Colony Logistics

Expand a single campaign beyond the home island by allowing players to establish permanent, fully buildable colonies on explored World Map locations.
Each colonizable location would have a predetermined island map. Before colonizing, players could preview its terrain, deposits, groundwater, oil, and buildable area. Once established, the colony becomes a permanent playable island that can be revisited at any time.
Only one island needs to run the full simulation at once. When leaving a colony, its resource quantities, storage capacities, and net production/consumption rates could be recorded. The inactive colony could then use lightweight background calculations instead of simulating every building, vehicle, conveyor, and worker. When returning, the calculated resource changes would be applied to the island.
Cargo ships could operate similarly to trains, but between colonies. Players could create routes that automatically transport resources between their islands with shipping rules, priorities, resource reservations, emergency shipments, and construction shipments.
All colonies would belong to the same civilization, sharing Research and Unity while keeping physical resources separated until transported.
Additional features could include:
- Colony specializations such as mining, agriculture, oil, manufacturing, and logistics
- Empire-wide resource and production dashboards
- Colony comparison
- Colony renaming, colors, and icons
- Colony templates
- Empire milestones
- Quick travel between colonies
- Ability to abandon colonies
- Construction shipments for establishing new colonies
- Direct resource transfers using cargo ships
The goal would be to turn the late/mid-game into expansion beyond the original island while keeping performance manageable by only fully simulating the currently active colony.
Instead of eventually finishing one island, the player's existing industry becomes the foundation for building an interconnected industrial empire across the Wor

Lightweight simulations would not be possible, because how you would calculate mining?