
This obsession with canals... (just teasing

)
--
The more I think about it, the more I am convinced that this "fortified trading-post" is in fact related to the new trade route concept.
As others pointed out, protecting trade routes effectively with units migth eat up the gains of the respective route (at least to a certain extend).
While my speculation above (regarding how those improvements could work) are not very convincing, I had some new ideas in the meantime.
I feel, that trading units will have at least
some defence against raiders. Maybe just as much as workers can defend themself when attacked.
What I can imagine are two possible game mechanics:
- a "traderoute-fortification-improvement" gives a bonus on this defence-ability,
when built on a tile that lies on the trade route. This will count to the traderoute itself and will not be dependend on where the caravan unit actually is attacked. Multiple bonuses could very well stack to represent heavily guarded trade routes.
- a "traderoute-fortification-improvement" gives a bonus on this defence-ability,
when the trading-unit is in its range (maybe 2 tiles).
I think, if this is not how the pictured building works, we
should have something like this...