And outside of chapters, BTG is fairly useless late game. So for secondary effects you have increased wholesaler offers (you don't rely on wholesaler late game, do you?
), reduced trader fee (you won't see trader fees once you hit a certain number of provinces) and ranking points (you can get these elsewhere cheaper). Not exactly exciting, to say the least.
So while I am not deleting my existing BTG (I have space), I probably wouldn't have built it nowadays if I had none yet. Vortex of Storage AW also has primary effect only useful in chapters, but at least it has secondary effect that is somewhat useful in the off-season (boosting sentient production). Even though this one is also a stretch