Since Blue Mage is a limited job and the chances of it becoming a real one are super low this would be my list.

Chemist as a healer would be great for a more technology focus healer and out of all the existing final fantasy jobs I think its the only one that can work in 14.

Mystic Knight/Spellblade is really the last known caster in final fantasy that can work in 14 if only because red mage while having some bits of it really doesn't go too much into it. It would probably be a caster but be a hybrid between both melee and caster with most of it time being up in melee positions and I think this would be best since we have 3 physical ranged and 3 magical ranged dps so really adding a melee would work but also having it different would probably be the way to go.

If neither of these jobs work I can only see them making new jobs yet out of all of them I think these two probably have the biggest shot of becoming the next two jobs unless Blue Mage becomes a real job later on which again probably won't happen.