Honestly what I like about ESO's rotating cast every major update/area release. You see some people again, sure, but not for a while - and not everyone always gets along or has the same motivations, personality, or temperaments. Makes groups feel dynamic and alive.
WoW has a bit of it too, though you have less of a 'party' and more a bunch of important people that come in here and there while you do more groundwork solo. That said, despite its own stumbling with writing lately, it still manages to make its groups of characters not all feel like the exact same alignment and motivation with minor personality quirks. Throwback to Turalyon being more than willing to kill Illidan after he blew up that overgrown chandelier the guy worshipped. We need more of that in FFXIV. Character conflict is good; keeps things interesting.
On that note, I'd like a chaotic neutral/evil-leaning character focused on 'ends justify the means' type of thinking. They don't need to be treated like our friend or even someone we trust, but adding varied elements of motivation and background and personality really does wonders for not making a cast grow stale over time. Much as I love the Scions, they've changed very little after each of their 'personal arcs' was finished up. Give them time to retire and let us meet new people, or explore further some we already know but have rarely had a chance to interact with long term.