Re-thinking trading posts, self-emerging cities

Rather than have trading posts replace cottages/towns etc, how about having trading posts serve a whole new function in the game?

Since roads cost maintenance in Civ5, long roads between two distant cities can be a drain on an economy. The re-imagined trading post could be built at one point along such a road, outside either/any city's radius, and offset the maintenance costs for road squares within a 1-2 tile hex radius.

These trading posts would also stand a small chance of turning into cities on their own over time, a bit like how barbarian-occupied tribal villages can turn into cities over time in Civ4. Throughout history major cities have often evolved from humble trading posts situated on trade routes between other, more established population centers.

They already kind of do. A worked trading post tile generate an extra 2 commerce.

What they can do is like the logging posts, increase commerce output in some way without breaking the game.

+1 will probably make trading post spam broken and be like a mini-golden age. But they can make is to that trading posts generation fractional gold which can increase gpt income.

The new kind of trading post I am talking about would only be buildable outside a city's big fat cross/hex. As such, they would never be worked by a citizen in any city and they would not add any yield bonus to their tile as that would be redundant. They would however cover the maintenance costs of nearby roads, so they could be built on roads or perhaps on rivers between two different cities so long as it's not enemy territory, not too close to any of your own cities, and not too close to another trading post.

Having this kind of trading post in the game would allow for cottages/hamlets/towns to be bought back as the main commerce-type improvement for tiles within a city radius.

It's said that many cities started as forts, then some merchants came selling stuff to soldiers or just opening shops and markets in a secure place, and some time later a city is standing here. Of course most forts don't ended like this but I heard many canadian cities began this way (maybe in USA too some cities are still called "Fort Something" for that reason). Just what I heard or read,no garantee.

I like the idea of cities not founded by settlers but by migrants, merchants or soldiers that settle down after a while.

Edit: most of the time I guess it's the commercial activity that bringed the rest in (when not a rich ground).