A lot of activists (including me) can be very passionate about the need to reach the unreached.
We talk strongly about the imbalance of missionary effort and the need to send more workers. We can blow a bit of hot air about why people aren't going to this place or that.
But we should all be very careful about this: when we talk generally and heatedly about the need for missions to the unreached, we can make people in specific feel bad about their own calling (if it's not to the unreached).
When we make blanket statements ("If you're not called to the unreached, then...") we can make people feel rejected, unvalued, unimportant, and even worse rebellious and disobedient.
The heat of emotion can even cross over into policies ("We don't support anyone not working amongst the unreached" and even "We've decided to restrict our focus only to the unreached and so we are dropping your support").
Policy decisions need to be made with care, and with plenty of time for people to transition. Remember, the fruits of the Spirit include both charity and self-control.
This is why, when I am teaching Perspectives, I go out of my way to intentionally say: "We don't have enough workers for the unreached. Now, if God's called you to go work with nominal Christians in London--you'd better not head to Nineveh! But if God's called you to the unreached--you'd better not be headed to London's nominals!"
If someone contacts me and says they are called to work with nominals in London, I will certainly help them find an agency, as much as it's in my power to do so. It won't be mine, but that doesn't mean I can't affirm their desire to obey and help them make connections.
Let's not assume our understanding of the remaining task trumps an individual's perception of God's calling on their life. They are personally responsible to God for their obedience--not to me, or to you, or to anyone else.