It's beyond far-fetched. Who in the family would acknowledge his authority? He'd be seen as a temporary outsider with no real power. Besides, this is to assume that there was nobody in this huge family that could assume that role and they had to send away for somebody. It's absurd.
If there is serious infighting, an impartial outsider everyone respected might be just the right person to prevent a civil war. The leaders would have to agree to make it work though.
