For me, it'd be Arenvald (although he'll need to trade in that wheelchair for a magitek one!), Estinien, Fordola, Hien, Magnai, Sadu, Riol, Jullus, maybe Gaius... even Gaia. Reposting what I said elsewhere, I'd really have loved a sundered Overlord travelling companion, if I am honest, particularly with Zodiark and the unsundered now gone (Emet/Hyth/Elidibus would've been my big choices otherwise) - especially if the Reflections are a destination, it'd be interesting to have one as a guide, with a revised agenda, since they were operating there.