it doesn't seem like Chrolo can choose the partner via the phone, he just set the conditions and the phone try to find the best suitabel partner.
The obviou plot twist would be Kurapika. Messing with kakin treasures may put the sussecion war in halt and the tension of the two of them to work...
There seems to be a lot of people that didn't like the ending due to the lack of explanations. Don't be like that, use your imagination to fill the gaps and enjoy the story!
Or does the fact that Edgar Allan Poe never explained why the crow only spoke nevermore annoys you too?