I may have said this before, but I think Trade routes are designed with the idea that you’ll always repeat and extend them. So, you go City A to B, and when the route resets, you go City A to B to C, with routes starting off internal (i.e. A and B are internal) but later becoming international (C is international). The changes to TR efficiency seems to play into this.
I wonder if Traders should actually “lock” to particular routes the first time you use one. So, in the above example, the first time you sent out a trader it would be locked as A to B. When it reset, it would have to go A to B again because it was locked, but you would have the option of extending the trader to C (ie A, B, C), but then that extended route would be locked - and so on. I think that would make selecting trade routes a more weighty decision.
If they did that, I think that would justify having a more flexible road system. So, TRs could still make roads, but perhaps you could also just gold purchase other roads between two cities if you don’t have a free TR.