Originally Posted by
dsaul
Just get the right rear derailleur.
The benefit of the Tanpan is being able to use an MTB derailleur on a gravel type bike with drop bar levers. This way you get the wider range and clutch of the MTB derailleur with a drop bar lever.
There is no benefit to going the other way.
Knowledge. I love it when someone has a perfect thread-killer answer.