So according to the guide that i trust for squadron-related info, youre partly right. Every recruit has 1 or more categories that interest them, and completing challenge log entries in that category gives you a chance to recruit them. The special condition mentioned under Gold Saucer, is that it can act as a wildcard for members of one clan per race. So if it works as a wildcard for midlander hyurs, that wouldnt apply to highlander hyurs. So not "any" recruit, but more then you might initially think. As for the recruit you named, Chrysabel looks like they accept PvP and Gold Saucer.

As for if the guide is accurate, i have no reason to doubt them though i havent personally recruited every NPC out there.