If SE decides not to give Jobs dual specs allowing a Job to fulfill 2 roles,they could just add Jobs that act as the foil like SCH & SMN. I have a list of jobs that could be tweaked to fit in;
(PLD)Mystic Knight-stat: INT & Skill Speed-Melee DPS that adds support buffs to the party for keeping up it's DPS chains.
(WAR)Berserker-stat: STR & Crit-DPS that increases damage as party members takes damage(within reason).
(BLM)Necromancer-stat: PIE-Heals by draining enemies HP and dispersing it to party members and can revive fallen party members as zombies on a timer.
(WHM)Geomancer-stat: INT-DPS Caster whose skill damage is based on the terrain and able to temporarily shift the elements to use other skills and add a damage buff for magic attacks.
(DRK)Rune Fencer-stat: STR- Melee DPS with a rune combo system that triggers certain elemental attacks and can add elemental debuffs to enemies.
(DRG)Templar-stat: PIE-Tank that uses auras to protect party members and do reflective and counter damage to enemies to keep aggro.
(BRD)Ranger-stat-DEX-Long Range DPS specializing in high single target damage and can also use traps to debuff the enemies.
(RNG)*Bard-stat-MND-Long range heals and support with songs that restore health, TP and MP.
Gunner*-stat-STR-Mid range constant conal DPS that specializes in AoE attacks relying on skill speed.
Cannoneer*-stat-INT-Tank that lowers enemies resistance to magic using various elemental shells
(MNK)Grappler*-stat-Vit-Tank that hold aggro and does damage through tethering skills tethering mobs can debuff the mob tethering party members can buff the party.
RDM-stat-PIE-Close-mid rage melee caster that can spot heal and add elemental buffs to melee jobs weapons.
BLU-stat-INT-Close-mid range melee caster that can temporarily draw skills from mobs and use them against them to attack or buff party members (set skills drawn)
Most of these jobs already exist in the FF universe and concerning the older jobs I feel eventually every job should be reworked to bring more utility to parties and raids.