Here's what I think is going to happen more often than not:
You'll be playing as China, which means you don't have as much control over when to trigger the ability. After a a trading post is finally established after whatever amount of turns, which you don't really know because the trade screen still doesn't show the correct amount of turns left (or did they fix that?), the ability will more often than not trigger eurekas and inspirations which aren't particularly useful, like apprenctiship or something like that.
Not only will you not be encouraged to build trade routes, you'll be encouraged not to build trade routes out of fear you might trigger the ability at the wrong time. It will make things frustrating for the player.
It will be easier when playing Mongolia, since you can choose the timing more appropriately.
Am I missing something?
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Honestly, imo they should remove the economy slot and just have the ability trigger with every trading post established. It's OP, but it's fun and unique.
Edit: Another approach would be to make it trigger with every new trade route. So each trade route level would trigger it once. (deleting and rebuilding a trade route would have no effect). This would encourage the player to focus one expanding the amount of trade routes they have.