Red Mage: I see this based on Gladiator/Black Mage/Monk... Astral/Umbral would last for 30s
30-- Umbral patch : burst area damage (enhanced damage based on umbral ice stacks.. NO enmity boost)
35-- Astra/Umbra-Shield : consumes astral/umbral charges to enhance defense (damage-spikes, or damage shield)
40-- Astral Flames : single target damage (enhanced enmity based on astral fire stacks), adds 1 stack astral fire
45-- En-Astra/Umbra : consumes astral/umbral charges to enhance attacks (extra damage, or MP) .. (alternatively en-umbral might place a damage down debuff on the target when you hit it)
50-- Faith of the Void : Grants 2 additional Astra/Umbral stacks of whatever element you currently have charged (1min cooldown)
So from Gladiator you would have
Fast Blade > Savage Blade > Rage of Halone (basic enmity combo)
Fast Blade > Riot Blade (MP recovery Combo)
Shield Lob
Shield Bash
Shield Swipe
Circle of Scorn
Provoke
Flash
Rampart
Sentinel
Bullwark
Tempered Will
Fight or Flight
Convalescence
Awareness
For CC-actions you could chose from...
Mantra
Featherfoot
Internal Release
Second Wind
Haymaker
Swift-Cast
Sure-Cast
Thunder
So you will have the basic Paladin toolkit for generating hate..
Single Target : RoH combo
Multiple Targets : Flash
Spending GCD actions on Astral/Umbral affects would allow you to enhance your attacks or defensive skills as needed with the en-astra/umbral or astra/umbral-shield. With a short cooldown booster ability it would require that you have at least spent 1 GCD on your stacks but would allow you to access more potent versions of the abilities much sooner.
It also would have 6 potential cross-class actions which are useful. Swiftcast & Surecast (good for getting off that astra/umbral spell), Featherfoot, Mantra (more HP when you get cured), and Internal Release (more damage), Second Wind (self cure) or Haymaker (slow the target) for an optional 5th skill
The major drawback is that Red-Mage would not have the shield-oath effect which Paladins have so they would be at an eHP disadvantage, although they would have access to the potent cooldowns and potential bonus from umbral-shield