First, support counsellor training programs, like the one I described that we're running that will train community members to be counsellors. Then you don't have to worry about flying anyone in and out.
Second, if we are flying people in, and there are reasons to fly people in, connect them to local counsellors and be colleagues. Be equal, be peers, don't treat them like “I have a Ph.D. and whatever, therefore I'm on a higher level”. No, everyone is a counsellor and needs to work together. That way, if that counsellor comes and leaves, the one who is a fly-in, fly-out, there are still people in the community who have a relationship with that person who is flying in and out, and they can continue to work with clients.