Leadership Training and Nationalization=Training and Empowering.
A supporting church once told a missionary, If you're not training your replacement, you're not doing the complete work of missions. And we won't support you. We agree, and see the vital importance of our missionaries training their replacements—equipping nationals to be the leaders. It's not about them being trained to lead during the absence of the American missionary. But, ultimately it's about them being the leaders in their local churches and ministries. The Holy Spirit picks the national leaders, and we do everything possible to empower them for their God-called work. He did that in Antioch, and He'll do it again, everywhere that He has a church.
Then it is the job of our missionaries to work in a support-capacity, as a helper to the national leadership that the Lord raises up. Last, they put themselves under the national leadership, doing whatever is needed to help them, only as long as is needed. Finally, as Paul did, our missionaries move on, to begin the same process somewhere else. And that's what we do.