God knows how they work now, but I think I know how they should work.
I've wanted a feature where you can customize where town food yields go, so you can stop supporting already large cities with low marginal growth rates, or alternatively, send all your food to such cities to help them grow faster. In order for this to not be totally ridiculous, I think there should be range limits and the best way to implement this considering the smaller size of some maps is so that you can send some food to a maximum range, and then as you get into a progressively smaller radius, you can send more (i.e.: food to 10 tiles, 50% to 20, limit of 10% of a town's food to a city up to 30 tiles away). This begs the question, how should settlement connections work in this context?
I think there should be a minimum connection range related to the trade route max range, and if a settlement is founded within this range of another settlement, they automatically connect by the shortest route possible to one existing settlement (being aware of open borders policies). Thus, connections can get cut off by loss of borders and don't automatically restore.
These connections are made once and only once. So, in this default situation, the distance from one town to a city will be the number of tiles the road takes up as it meanders to settlements on its way to that town. If this puts a city out of range for food delivery, then you can use a merchant to form a direct connection. Think of a triangle, where the indirect, default connection are the two sides, and the direct connection is a shorter total length hypotenuse.
On top of this, to give more logic and control to the hub town concept, a town will add a distance modifier to all its connections based on the number of connections it has. That is, town A gets -1 calculated route distance per connection greater than 1. So, if town A has 4 connections (even if they were established by default) to towns B, C, D and city F, of lengths 8,7,12,6, then the modification of -3 makes those lengths be calculated as 5,4,9,3. This means the route from town B to city F used to be 8+6=14, but now it's 5+3=8 and therefore underneath the 10 tile 100% food range. The thematic logic is that these natural hub towns have more caravan support infrastructure and experience and they are transporting goods more efficiently.
This system will make connections more logical, more of a sub game in themselves, and support the premise of customized and strategic disbursement of food to cities. It will also fix hub towns.
Sea routes should function in a similar vein. This "all connected to all, but not all the time, and it's often bugged" connections system needs to go.
Logical connections also creates a gameplay stratum that can support added content like non-settlement trade outposts in special scenarios like silk roads.
Trading towns will differ from hub towns in that they extend connection range without requiring multiple connections. If you do multiple connections to a trading town, you may make its natural route distance boost irrelevant, while missing out on the influence bonus from hub towns. That would be the trade off.
I've wanted a feature where you can customize where town food yields go, so you can stop supporting already large cities with low marginal growth rates, or alternatively, send all your food to such cities to help them grow faster. In order for this to not be totally ridiculous, I think there should be range limits and the best way to implement this considering the smaller size of some maps is so that you can send some food to a maximum range, and then as you get into a progressively smaller radius, you can send more (i.e.: food to 10 tiles, 50% to 20, limit of 10% of a town's food to a city up to 30 tiles away). This begs the question, how should settlement connections work in this context?
I think there should be a minimum connection range related to the trade route max range, and if a settlement is founded within this range of another settlement, they automatically connect by the shortest route possible to one existing settlement (being aware of open borders policies). Thus, connections can get cut off by loss of borders and don't automatically restore.
These connections are made once and only once. So, in this default situation, the distance from one town to a city will be the number of tiles the road takes up as it meanders to settlements on its way to that town. If this puts a city out of range for food delivery, then you can use a merchant to form a direct connection. Think of a triangle, where the indirect, default connection are the two sides, and the direct connection is a shorter total length hypotenuse.
On top of this, to give more logic and control to the hub town concept, a town will add a distance modifier to all its connections based on the number of connections it has. That is, town A gets -1 calculated route distance per connection greater than 1. So, if town A has 4 connections (even if they were established by default) to towns B, C, D and city F, of lengths 8,7,12,6, then the modification of -3 makes those lengths be calculated as 5,4,9,3. This means the route from town B to city F used to be 8+6=14, but now it's 5+3=8 and therefore underneath the 10 tile 100% food range. The thematic logic is that these natural hub towns have more caravan support infrastructure and experience and they are transporting goods more efficiently.
This system will make connections more logical, more of a sub game in themselves, and support the premise of customized and strategic disbursement of food to cities. It will also fix hub towns.
Sea routes should function in a similar vein. This "all connected to all, but not all the time, and it's often bugged" connections system needs to go.
Logical connections also creates a gameplay stratum that can support added content like non-settlement trade outposts in special scenarios like silk roads.
Trading towns will differ from hub towns in that they extend connection range without requiring multiple connections. If you do multiple connections to a trading town, you may make its natural route distance boost irrelevant, while missing out on the influence bonus from hub towns. That would be the trade off.